How to make custom doll shoes?

I've always loved sewing clothes/outfits for my monster high dolls, and I've gotten back into it recently after buying some of the new g3 dolls. The problem is that none of their shoes really match the outfits I've made, and none of the g1 shoes I have/can find online will fit the g3s. I'd love to make my own shoes, but I'm not sure how.

Does anyone here have any experience making custom doll shoes? What materials are you using/how are you doing it?