For me the next step should explore how to cut out the firing part of the process altogether, pottery looks cool but the process requires a lot of energy. Perhaps it could be done on a piece of wood planed by hand? You can get those fairly flat. Then use copper tape (or laminate your own copper really) with some homemade adhesive?

Actually now that I think about it you could just make pine rosin (pine resin + alcohol) as your adhesive. For the copper laminate this might be harder without steel rollers or a way to cut.