PARIS, France — When Isabel Marant was studying fashion design at Studio Berçot, the school's director, Marie Rucki, gave her an invaluable nugget of wisdom. "She told me to never design anything that I wouldn't wear myself. That influenced my work from the start and gave me a realistic approach that continues to inform what I do," the designer told BoF.

Indeed, influenced by Rucki’s practical piece of advice, Marant has built a business that, over 20 years, has seen consistent annual growth rates of between 20 and 30 percent and, in 2013, generated €150 million in revenue according to Marant’s chief executive, Sophie Durufle. The same year, a major collaboration with H&M confirmed the label’s heavyweight status, an achievement made all the more impressive by the fact that Marant retains full ownership of the company.

Often described as chic in a way that manages to be both bohemian and a little rock 'n' roll, Marant's clothes are essentially American-style sportswear filtered through a uniquely French sensibility, which gives them an insouciant edge that is equally irresistible to women in Los Angeles, London and Seoul. The mainstays of this look exemplify Marant's magic mix of ease and attitude: slim jeans and t-shirts, peasant blouses and lace mini-dresses, fringed boots and bags.

As she tells it, the designer’s rise has been slow and steady — and very much a family affair, by which she means, not only that the company remains under her control, but that Durufle is Marant's former sister-in-law. The recipe to her success? A well-defined, consistent aesthetic rooted in boho-chic, Parisian cool; clothes that blend fashion-forward design with wearability, advanced contemporary pricing, and, last but not least, Marant’s own relentless drive. “Isabel is the first one to arrive [at work] and the last one to leave,” says Durufle.

But, perhaps more than anything, building Isabel Marant has taken extraordinary clarity and focus.After finishing her studies at Studio Berçot, Marant chose not to work as an assistant for an established designer. “I had a very precise idea of what I wanted to do and I was totally determined to do it myself and not work for somebody else. I started with a jewellery collection because I could not afford to launch a garment collection,” Marant recalls of her start, back in 1989. She says she inherited her fearless drive to do her own thing from her parents. “My father and my mother both ran companies, so I grew up surrounded by this idea that if you really want to do something, you can do it.”

Traction came early for the designer, though at first the brand remained something of an insider's secret. “When I launched my own [fashion] label and started doing shows in 1994, for the first couple of years my audience consisted only of my friends. No journalists came, because what I did was nice but not eccentric or historical. What my peers were doing was perhaps more intriguing, but it couldn't sell,” she adds. “I may have not been in the newspapers, but I was selling from the beginning, while others weren't and spending all their money on these extravagant shows, just to create an image.”

Marant says eschewing editorial attention was a strategic choice. “I knew how to attract press, but I firmly believed in first settling my company and making it work and only then doing something more fancy to please editors.”

In the beginning, Marant attracted a local following solely through word of mouth. “At first, we had no selling points in France. I would just have these private sales in my living room for friends. They, in turn, would bring their friends and so on. Before too long I had 400 people showing up.”

But a Parisian insider's market alone was not enough to jumpstart her business in a significant way. What really propelled Marant's label early on was the Japanese market. “We were lucky; we had Japanese retailers. That was massive and helped my brand a lot. They placed huge orders.”

“The only way we were able to handle the demand is because the clients were paying in advance," Marant recalls, explaining how she was able to get around the cash flow issues that often plague young designers. “I asked them to pay me before delivery, as soon as the order was confirmed, which allowed me to invest into the buying of the fabrics, etcetera.”

Part of the reason why Marant's collections were so well-received from the start was the fact that her aesthetic stood out from what was prevalent in fashion at the time. “What I was doing was different from the kind of super-clean minimalism, very influenced by Helmut Lang, that you saw everywhere,” she says. “My stuff had a strong ethnic element. I think that resonated, along with the comfortable fabrics and special colours that are still close to what I am doing today, even though my collections have evolved as I have evolved.”

Only after laying the commercial foundations of her business did Marant feel it was time to develop her brand. “Before getting too big too quickly, we wanted to build stone by stone, being very reasonable and taking our time to set up things, so that the base was strong,” says Marant. “Only once the company was operational and we had a clientele were we ready to work on image.”

Though the label had traction from the beginning, things really took off in the mid-aughts, a turning point Marant credits to making two critical hires in styling and PR.The shift began when Marant asked the French Vogue editor Emmanuelle Alt to style her shows. "At first I didn't dare to ask her, I admired her so much," recalls Marant. "But when I did (through Alt's husband, the art director Franck Durand), we had so much fun together. We are exactly the same age and have the same fashion culture, so it was natural to collaborate." (Alt, who is now editor-in-chief of French Vogue, styled for the brand from 2007 to 2011).

Since the company's inception, Marant had been working with the same press officer, out of loyalty and because she had taken Marant on for free when the company was just starting up. But as her label began rising in profile, the front row of her shows remained curiously devoid of key international editors. After styling two shows for Marant, Alt told the designer she needed to reconsider her press representation if she wanted to continue working with her. “She said, ‘Style.com is not at your show, nor any of the important press people from around the world. That’s not acceptable at the level you have reached.’”

Fearful of losing Alt, Marant engaged the press agency she still works with today. "I had no idea at the time how important the press office you work with could be. In just one season the audience at my show totally changed." Durufle adds: "[The change] was more in terms of visibility than numbers, because the numbers were strong already. We had a good business, thanks also to Étoile," Marant's diffusion line, which launched in 2000. But just as important as this was Alt's styling, which added a vital injection of sex to Marant's work. "Emmanuelle put Isabel's woman on heels. That changed everything," says Durufle. Marant concurs, "The clothes didn't change. But Emmanuelle came with a pair of tight suede cuissards (thigh-high boots). That small decision totally changed the way the clothes appeared and how my label was perceived. It made it much more glamorous and sexy."

At the time, while Marant's label was well-known in France, Italy and parts of Asia, it had little presence in key markets like the US and UK. Indeed, after the changes to styling and communications, US expansion was another key catalyst for the brand. The designer opened her first standalone New York store in 2010 on the heels of what had already been rapid wholesale growth in the American market (which today accounts for about 30 percent of the Isabel Marant business). Fortuitously, the expansion coincided with a the culmination of a shift in women's tastes, away from the over-sexualised aesthetic of the early 2000s, as epitomised by Tom Ford's Gucci and Yves Saint Laurent, and towards Marant's earthier, boho-chic look, which was still sexy and sophisticated.

Much has been made of Marant's biggest hit product, the ubiquitous hidden-wedge sneaker known as the Bekett, which the brand launched in 2009 and has reissued every season since. But the designer underplays its importance as an engine of her success. "It's the whole silhouette that has come to define me and people ask for, not one particular item," she asserts. Yet the numbers speak for themselves. At the height of the sneaker's success, in a single week in Paris alone, Marant was selling over a hundred pairs of the shoe. Now, it's down to ten. (Famously — and to Marant's chagrin — the shoe has been copied by everyone from Michael Kors, to Hogan, to Adidas).

Today, accessories account for 30 percent of Marant's business. Her biggest markets, besides the Unites States, are Europe and Asia, where the label has a particularly strong presence in Korea. In recent years, online sales have driven significant growth for the brand, especially in the United Kingdom and Germany. In fact, Isabel Marant currently generates 40 percent of its revenues online, though the company still lacks its own e-commerce store. As for the future, the US market remains a key focus, where Marant plans to expand its retail network, opening a new store in San Francisco in the coming months.

“Build a strong base and stay focused and true to yourself. Find out who you are and stick to it, because you need to have a specific and understandable message that is uniquely you. And never design anything you wouldn't want to wear yourself."