There's a small section in the U.S. Air Force Search and Rescue handbook called "Firecraft undder evasion conditions." It talks about the use of a Dakota fire hole or a trench fire. The Dakota fire hole is made by digging two pits, then joining them with a tunnel at the bottom. You build the fire in one pit and air is drawn in down the other pit and through the tunnel to supply the fire.

The trench fire is simply a trench dug into the ground to put your fire in. The book talks about this being most useful for a group of survivors needing to do their cooking.

One thing the book mentions is that a fire that needs to be concealed should be kept small and used only for cooking, not heat. Also, make sure to bury any unused firewood.

I got the U.S. Air Force Search and Rescue handbook here, or go to the Publications page here at ETS and several of the books available there online have diagrams of the Dakota hole and other useful information.

By the way, I have not had a chance to try these out. I have the book sitting here next to me as I type this.