I've been searching high and low for a decent gf playdough recipe, and this is the best one I've tried by far....
2/3 cup maize flour
2/3 cup besan (chickpea) flour
2/3 cup rice flour
1/2 cup salt (table salt is best)
2 tbsp canola oil
4 tbsp cream of tartar
1 1/2 cups warm water
Chuck everything in a saucepan and stir it until all lumps are gone before heating. Cook over low heat and stir often- this takes a long time! Leave it to sit until pretty cool - it will get less sticky.
* This seems to take more cooking time than "normal" playdough - it needs to be cooked very thoroughly.