I bought two trash cans (on wheels) to reclaim some hard clay donated to my
program from one of our other buildings. I put as much of the hard clay as
possible into the containers - poured water in to the top edge of the
clay -- then let sit for months. I kept checking and added more water until
clay was ready to use. You can wedge clay onto a plaster slab if you have
one -- I just used canvas covered boards. I haven't gotten around to making
the slab wedging board yet - I keep meaning to order plaster for it. We
have been using this reclaimed clay now for a couple of years.