First I cut a rough hand shape from Pink Styrofoam. I cut a second identical shape from
blue Styrofoam and glued them together with a wire support for the hand and each finger

In this photo you can see the pink and blue Styrofoam. I have started to rough out the palm
and have shaped the thumb bones.

Here is the partially finished hand, thumb in foreground.You can see I have coated the
hand with a thin coat of plaster as I finish the rough shape.
This permits me to sand the bone to the finished shape I desire.

Here is the finished hand, ready to attach to a forearm.