I made a powder coat oven using plywood sheets on the outside. I use one 1500 watt lamp with a hole cut in the plywood to fit the lamp. The inside is insulated with aluminum insulating sheets and sealed. I also put a temperature probe inside connected to a temp control unit. I've been able to get up to 450 degrees %F with no problems.That was three years ago and it still works great. The cab size is 24" square 50" tall.
Should be easy to make.