Have been saving this for awhile and hope to make this soon. Wondering If I should line the base with some firebrick or just use the earth? We have some stone that has been laying around for years - believe it came from an old stone wall in the woods and dumped here by the previous owner. I hear you have to be careful about using river rock as they could explode if stone retained any water - certainly don't want any exploding rocks. Thought I would share Scotty's sketch for others - he previously posted it.