Modifying the oven floor

The  image below shows an early attempt of making pizza in the oven in 2009.  I spent a lot of time constructing the fire arch for syrup season last year. In the late autumn I decided to try the oven for cooking  pizza. So using our existing pizza stone I placed it on top of the fire grates to form the floor of the oven.

While it served it's purpose well it didn't survive the harsh temperature changes of being outside. So I went  into this season planning to put in a floor consisting of fire brick. To make a level surface, I placed a  piece of sheet metal cut to fit the floor. Next I used sand to level the bricks. This worked pretty well but after 5 hours of fire in the hole the bricks became slightly uneven.

I attribute that to the metal heating up and buckling up slightly. My next fix will to get some refractory insulation board and place that on top of the sheet metal then place the brick on top of that. I may still need to put a 1/2" of sand to stabilize the bricks.

From the outside, the  whole unit was warm to the touch so I'm also going to put a layer of the insulating board on top and on the backside of the rear wall. Without major revisions to modify the side walls, they will remain as is.