MOUND FIRE

If you practice the principles of leave no trace but love spinning yarns by a campfire, try building a mound fire the next time you're in the backcountry.

Construction of a mound fire can be accomplished by using simple tools: a garden trowel (AKA poop trowel), large stuff sack and a ground cloth or plastic garbage bag.

To build this type of fire: Collect some mineral soil, sand, or gravel from an already disturbed source. The root hole of a toppled tree is one such source. Lay a ground cloth on the fire site and then spread the soil into a circular, flat-topped mound at least 3 to 5 inches thick. The thickness of the mound is critical to insulate the ground below from the heat of the fire. The ground cloth or garbage bag is important only in that it makes cleaning up the fire much easier. The circumference of the mound should be larger than the size of the fire to allow for the spreading of coals. The advantage of the mound fire is that it can be built on flat exposed rock or on an organic surface such as litter, duff or grass.

-Taken from LNT

Here you can see the ground cloth and classic orange poop trowel in action. (source)