I have called all over around here and can't find plain fireclay. I need to level the vermicrete pad so i can lay the floor. As I understand it. the fireclay that is called for is not refractory cement so it would just be an underlayment of powdered clay to level out the pad. I saw on here that someone reccomended using the dried mortar but my concern would be that the floor bricks would set to it and that would mean that I couldn't swap out a broken brick later on. So I can't find the clay. How about digging up red clay and using it? or how about using sand or some other material . Help me out. What should I be looking for to take care of this?