Hmmm, I think I am confused by the many types of clay/plaster materials there are. Okay here is what I was thinking about.
Yes, the pots would have raised designs. I was thinking of something that you mix powder with water and pour it into your mold. You don't have to bake or oven kiln the project when it dries. You can paint it when dried and varnish or polyurethane when done to protect it.
Does this make sense to you?
Wildflower