Protalwell Woodstove Firebricks, Upgrade Fire Bricks Replacement for US Stove FBP6, Size 9" x 4-1/2" x 1-1/4", 6-Pack

I started off that way but the bottom would burn before the top cooks. Raising it off the grates will give you reflective heat from the top and gives the bottom time to cook. The bricks are rated up to 2200 degrees from Amazon.