TYPICAL OVEN ASSEMBLY: On a flat, stable surface, mount two support legs using 15-cm cement blocks and lay a 10-cm-thick reinforced concrete slab.  Prepare a 2- to 3-cm-thick layer of lean mortar on which you mount the oven sole, verifying that it is perfectly flat. Mount the oven without mortaring the joints. Build a wall around the oven using 10-cm cement blocks. Mount a flue with inside dimensions of 20 cm x 20 cm. Surround the oven with a 5-10 thick layer of rock wool, then cover it with about 10 cm of sand or vermiculite concrete. Build a roof over the oven and add the desired trim.