Stolle will work on the design of the website with the Rehabstudio team over the next six weeks. It will go live during September's London Fashion Week.
The competition was open to designers involved with the non-profit Fashion East project, which champions emerging talent.
During May and June, the designers were asked to bid for a chance to win the prize by submitting ideas for their website.
Rehabstudio's creative team selected a winner based on the most inspiring pitch.
Tim Rodgers, creative partner at Rehabstudio, said: "Natascha's pitch stood out for us because it was sassy and creative. She's a great designer and she gets digital.
"She came up with a quirky concept for what she'd like to do online which has a really nice cut and paste, laid-back feel to it which fits perfectly with the way we hand craft our designs.
"It's great that she's engaging with the medium properly, not just putting a glorified look book online."