I have been making a LOT of charcoal using the PYROMID method: Stack up a lot wood (as from cutting up a brush pile for instance) in a DENSE pyramid, any size. Use tinder to light the apex of the pyramid at the top.
The reaction zone will quitely ignite layer after layer with the upper layers of charcoal protected from burning by the expanded layer of deoxygenated ("dephlogisticated") gas rising by natural convection. Avoid windy days that would blow the protective gas sideways.
Stand by with a hose of watering cans to wet any char that extends beyond the protection and to put out the whole pile when done. After you think it's out, think again because small embers can hide and come alive again.