Then, a couple of years ago, the marriage fell apart, and Ms. Legras, who is now 33, set out to follow the bags’ advice. She closed her shop, put all her possessions into storage and, in December 2024, moved to a 400-square-foot apartment in the Marais district in Paris. There, in a single room with antique ceiling beams and terra-cotta floor tiles, she eats, sleeps, does yoga and runs a company called Boxwood Avenue that is part design studio, part e-commerce business, part influencer platform and part tour operator arranging shopping trips in France, the U.K. and Italy.