Jamie Haller loafers are fashion lore. Can she do the same for sneakers?

At $600, Jamie Haller loafers aren’t an impulse buy, but they’ve become one of those rare fashion items people evangelize anyway. The shoes, which resemble classic men’s leather loafers, have quietly built a cult following thanks to a surprising claim: Fans—from TikTokers to Wirecutter—say they mold to your feet the moment you step into them.

This didn’t happen by accident. The Los Angeles-based designer spent years seeking out a factory that would be willing to make her loafers using sacchetto construction...