You can make them out of about anything. I made my last one I hope, it's 4 x 4 prob 6' tall, above two & 1/2 blocks, with two screens in it about eye level. I used fire brick on the floor for a fire inside the house. I made mine tall in case I wanted to smoke sausage. I framed it with 2x4's sheeted it with cull cedar boards from a local mill. I have smoked all kinds of meat in it. I can take some picture but still having trouble resizing them.
you can also make the fire pit outside of the house & pipe smoke in for cold smoking. Ed