Clay bricks are an alternative building material to fire bricks for building a pizza oven. If you are seeking to use this material, you can either buy readymade clay bricks or make them yourself. To make your own clay bricks you first need to make the earth mortar then using a frame, make the bricks to a desired shape. The typical shape is rectangular. After they have dried, bake then using a brick kiln.
These baked clay bricks are ready and they are used with cement mix or clay mortar to make the pizza oven.
Further information: Build a wood burning clay pizza oven and Clay oven pizza