The liners are like an inner bootie, not just a flat piece of felt on the bottom. But it could be done if you could find felt thick enough.Glad you were finally able to get/try (and like) Wendy's chili... I haven't had it in many, many years due to past experiences but maybe I'll give it a try next time I stop there. As for their frostys... IMHO they leave a LOT to be desired... But who knows, maybe you'll find them acceptable. I guess a lot of folks like them. I prefer a real ice cream shop and a real milk shake (or frappe if you prefer).
Perhaps buying a new pair of boots would prove cheaper? Or just buy some felt and cut out your own?