I found a demo that describes in pictures what I tried to say in words. This is far more effective. I don't have the plans on how to make a hotbox, but I know that it involves finding heat bulbs and that it is important to have anodized aluminum (which is pretty pricey).
I have seen people learn how to use this technique by working on a pancake griddle. Walmart currently have two flat griddles that are $19 and $35 according to the size you want. The surface is just like you would find on a frying pan. I have been thinking that if you buy an indoor grill, you could buy a small sheet of the anodized aluminum to make sure you have that smooth finish as we see on the movie below.