I bought the 36" Pompeii kit, and have the insulated FB board down and the 18"x18" floor tile cutout to the 36". So the cooking floor will be inside the oven dome. The plans say to lay floor tile to the fb board with the paste 1 part fine sand 1 part fire clay. The question is do I use same paste for dome? Or do I use fire mortar? And do I also lay first course of brick directly on the fb board?