Beautiful Vase.Maybe try Chinese carryout box for template on small vase or pencil holder.With one piece clay cut out and fold up and slip .Might work?
I used porcelain Standard #365. I really did not let the clay set up much before working it although my clay can be a bit dry coming off the block and that can help. Did they tear in the fire? If so, are you reinforcing the joints a little?
