Hi! Great looking oven by the way. im building a pizza oven using storage heater blocks for base (with thermolite blocks under those). I've got a couple questions if u don't mind. How do I bed the thermolite blocks and heater blocks in? Sand/cement etc? Also the storage heater blocks aren't flat on one side ie a cavity. I think these these are referred to as slips or frogs??!?? Do I need to follow this cavity in before laying? Any advice would be great thanks.