Just a note for others. If you do use a trench, or hole for a fire, be careful that the soil/ground is not such that you may start an underground duff fire. It is possible to put out ones main fire and not realize there is a smoldering fire traveling horizontally away from the the original fire. The best place to do a fire of this sort is in mineral soil. An easy place to find it (at least in the Northeast US) is at the base of an uprooted windthrown tree. An added bonus is the natural windbreak of the root wall (though it usually doesn't block the prevailing winds.

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