Small, thin items warping?

Once upon a time, someone was making polymer clay rings, and they kept warping while being baked.
We determined that this was due to uneven heating, because these rings each sat above one or more lines of the metal whatchamacallit (that you slide out and set trays, etc. on in the oven). Once the baking sheet was raised at the corners so the lines no longer touched it, the rings did much better.

Beads don't usually seem to run into this problem. But in case you ever make a thin polymer clay donut bead, and it warps, try making sure there are no hotter & cooler stripes under your tray!

Safety Notes:
Althought polymer clay is non-toxic... we recommend that you don't use your eating cooking utensils for polymer clay and vice versa.
And if you are doing more than an occasional just-for-fun polymer clay piece, it is also recommended that you invest in a second oven (So, go into the polymer clay business, if you need a good excuse to get a new oven for your kitchen, and use the old one for your polymer clay!)