Skiing in a pair of well-fitting boots in bottomless pow is snow-sports nirvana. And ill-fitting boots? Well, that’s undisputedly the opposite painful and unresponsive regardless of conditions. Making sure your feet have the room they need to flex, swell, and stay warm, all without sacrificing the stiffness your boots need to effectively drive your skis is critical to enjoying your time on the slopes. And because no factory fit is perfect for everyone, you’ll probably need some way of molding them to your feet. Here’s how to do it yourself with a few variables to consider before you start.