How do you make 3D castings from a flat- backed push mold? The shape of the casting would need to be symmetrical, or it won't match-up when you make two and flip one around to the back side. One way around this would be to leave enough clay on the flat side of the mold to round out the shape before removing it from the mold and try to shape it out by hand. This would take some talent, but it would be an option.