We picked up an unglazed 12 inch terracotta tile at the big box store to use as a baking stone. it works great for in a pinch and it is 3.00. this was because I had a brain cramp and thought I had one for the large and didn't and the local dealer did not have any :(
Neil is going to cut the corners off and grind them a little. it can not be any worse than cooking in the plant pots??