Scrape out a trench in the dirt about a foot wide and 8 inches deep. Line it with very dry, egg-to fist-size stones (wet rocks from a stream or lake can explode when heated).
 Next, burn a fire down to coals and spread a layer throughout the trench. Cover this with at least 4 inches of dirt and tamp it down with your boot. Wait one hour. If the ground warms in less than an hour, add more dirt.
 Check the area twice for any loose coals that could ignite a makeshift mattress. Then spread out a groundsheet of canvas, plastic, or spare clothing. Pine needles or evergreen boughs will work in a pinch.
 Ease onto your fire bed and snooze away.