Choose a level area that is as sheltered from rain, wind and snow, if possible. You will have to dig about 1 foot beneath the surface, so it is preferable to select a site without an abundance of rocks, roots, ice and snow. Also, if you find that there is water close to the ground surface, you will have to find another location.
Gather dry fuel with which to build your fire. Look for hardwoods over softwoods, as these will provide the long-lasting coals you will want to keep you warm through the night.
Gather a good amount of dry insulation which you will find in the form of pine needles, leaves or grass. Especially if you lack sufficient warm clothing, this material will prove vital to keeping you comfortable.
Dig your trench to be about 1 foot deep, 1 or 2 feet wide and slightly longer than your own height. Whether you have a shovel or you are forced to use a knife or a sturdy stick--or even your hands--this amount of digging is possible if you select your site well.
Place baseball-sized dry rocks along the inside edges of your pit, spacing them about an inch apart. Although the rocks are not necessary for your fire bed, they are put there to provide more air space so your fire will burn longer.
Using a firesteel, light your tinder and hardwood inside the trench to begin a steady fire. You could also use a lighter or matches, but since a firesteel works in all types of weather and will never run out of gas or sticks, it is the ideal tool for starting a fire.
Spread the fire across the length of the trench and keep it burning for 2 to 3 hours. Your goal here is to produce a string of hardwood coals.
Cover the entire pit with dirt and compact it to about 4 inches above the level of the coals. You are ready for the next step if the surface of the soil becomes warm to the touch after about an hour. If it becomes warm sooner, pile another thin layer of dirt on top of your bed or it will become too warm for you to sleep on.
Place your insulation on top of the bed, preferably between two or more logs which will serve as windbreakers while preventing your insulation from sliding or blowing away in the night. When you are ready to lie down on your bed, place a thick layer of insulation on top of your body and enjoy your warm sleep.
