One Man's Rubbish...

The next time you see a discarded microwave oven set out for trash, check to
see if it still has the glass plate inside. I've found that glass microwave
plates make the perfect working and baking surface for polymer clay.

Cake containers (the kind with a plate and a cover) can also come in handy when
working on medium-size sculpted pieces -- especially if you need to transport
them while still unfinished. The cover helps protect the piece and ensures
that it stays dust-free. I have an old plastic one with a knobbed cover that
slide-locks into the plate; you can probably find inexpensive ones like this
at garage sales, flea markets or bargain stores.