I have a top loading Big Chief smoker. I take the rack out and set it on top of the smoker on the lid. I place the cardboard box that the smoker came in over the top of the rack. It extends down far enough to cover some the smoker as well.
I place the pan of chips in through the front access door and let it begin. The Big Chief lid has vent holes in it so the smoke rises up into the cardboard box encased rack.
The temp holds around 90F for me.