This was made from three scrap pieces of styrofoam insulation stuck together. It was
shaped freehand with a serrated knife, then the foam was wrapped with strips of wet
newsprint applied with white glue diluted 50/50. Several coats of latex paint thickened
with drywall compound were used to get a plaster-like surface. There are even two one
inch high wood blocks glued to the underside to elevate the edge for tooling and trimming.

Two caveats: Allow for about 15% shrinkage and do not let the clay dry over the
form, as the clay will shrink and crack as it dries.