Hello all. I have been lurking on here reading some geat ideas. I wanted to build my first oven, and wanted to see if anybody has experience with A flat roof design versus a dome. I was looking at building a 40 x 40" square 20 inch tall with the small door section. The walls being 3 1/2 inches thick blast cement. With this design work well or would it be a waste of time? Thanks for the input