I need a new cast for feet that will hopefully get a few dozen uses out of it, so the first step was to make some soft, unbaked sculpey feet, and get them in a container just the right size (as I had no potter's clay to make a mould), then smother them in a thin layer of vaseline (as a release agent). Next, mix up the plaster of paris, and (stirring it slowly and gently to keep the air bubbles out) and pour into the mould at leave to set. I also added a pair of wire handles into the plaster to allow myself something to grip when trying to remove it from the tupperware mould.