First one I built worked quite well. I built a plywood box that was 2'x2'x4'. I didn't need to do it.. but I lined the inside with sheetmetal. Drilled a bunch of 3/8" holes in the top for circulation/ventilation. Actually, the door fit loosely enough that there was enough ventilation.
Installed a hotplate in the bottom and added a small thin frying pan to it. Added wood and covered with an old moon type hubcap to ensure smouldering vs flameup. There was a bottom door that was easily removed without losing heat in the top. This allowed addition of more wood as needed and adjustment of the hotplate for cool smoking vs cook smoking.
Shelves were simply pieces of 1x1 fir that had screen material tacked to it. Not pretty but worked. IF, IF I ever build another, I'd find a bunch of same sized stainless grates from an old refrig or maybe even the grates that are used to cool cookies or bread.. and build the box around those.
It worked pretty dern good.. but my 008 is far more efficient... and looks a bunch better