The mould released from the plywood base but just broke the foam blocks off. The one on the left is where I've tried to dig out the foam, but I can't get it all out without gouging the hell out of the mould surface. I don't know if this was just because the wax wasn't good enough to release a more complicated shape or if the join between the foam and ply wasn't strong enough to withstand the pull. So this time I've made the blocks out of wood as well and screwed them onto the base. I made sure the sides were cut to 10 degrees to make sure the angles aren't too tight.