These drawings use a popular aluminum lithograph plate from a #102 Heidelberg press, 770mm x 1030mm x 0.3mm. This and other sizes are available from government and commercial printers or newspapers. They are sold for the price of scrap aluminum, about $1.25/kilo. Staple or rivet small plates together to make any size unit. We can help design cookers for other plate sizes.
Note: 30- or 32-gauge galvanized steel, stainless steel, or sheet metal painted with a reflective paint will work. Sheet metal costs and weighs more and is harder to cut and bend than printing plates. Sheet metal does make a stronger case.