I once decided to try if I could make doll shoes using polymer clay. I was using Cernit, because I like it better than Fimo, which tends to get too soft in my hands.
First I formed the clay into a fairly thin sheet and then used a paper pattern and hobby knife to cut out the soles of the shoes. I used the heel part of the same pattern to cut two pieces for each heel. If the clay is difficult to cut neatly, place it in the fridge for a couple of hours to harden. Then it should be easier to cut. Also, the knife needs to be sharp.
I smoothed the edges of the soles, placed the heel pieces in place, and used the doll's feet to check that the form of the soles was correct. Then I baked the soles in the oven. When the soles had been baked and cooled, I added the insole, strap and small decoration.
The insole is probably more important here than when using other materials. Polymer clays have bright colors, so if they stain the doll's feet, it will certainly show. I'm not sure whether they stain or not, but I prefer caution and use an insole that insulates the doll's feet from the clay.
This experiment gave me an idea to try to make an entire shoe out of polymer clay. It should be fine, if you bake the sole first, so you don't need to be too careful with it. Then you could build basically anything on top of that, provided that you take care to check that the shoe will go on and off easily as this kind of shoes won't stretch at all.
It's been a while and I still haven't got into trying that, but maybe I will at some point.
Original Finnish post: January 25, 2006