Reply by jmos

The built-in’s I’ve seen (like my Sisters) are surrounded by the same material as the rest of the cabinets. The oven should be pretty well insulated. The sides should get warm (~100-120deg F), but not really hot (over 140Deg F, which is usually the point where you can’t keep you hand on it).

My kitchen, with a regular slide in stove/oven combo has cabinets butted up against each side, and those cabinet sides are your basic particle board with a picture of wood glued to it construction.

I would think plywood would work fine.

-- John