Select some sort of stake (hammered into the ground) or more robust steel/cast iron/ whatever "stand" that can hold the turkey sort of like standing on its butt (would be interesting to do this with the "beer-butt" cooking method) .
Place a (new) stainless steel garbage can over the bird (you could use cast iron, but if using galvanized metal, burn it out first).
Around the sides of the can, bank with 10-12 lbs of charcoal briquettes, (fully grayed up) and cover the top of the can over with a layer or two of burning briquettes.
Allow to cook for 1.5 hours (for a smaller bird) to 2 hours for a larger one, periodically "dusting" the briquettes and re-banking them. (No "peeking" obviously!) .
On conclusion of the cooking period, sweep away the remaining embers and ash, and very carefully (anticipating a pretty vicious blast of hot air and steam) and test your bird that the required parameters of 160 in the breast, 180 in the thighs (okay, you can do it 10* less, as it will convect up that much, no point in it being too dry).
If you want, there can be all sorts of "tweaks" -- you can in fact "beer butt" it, with a large soup can 3/4 full of onion soup/beer/cranberry juice/herbs/spices, pick you own poisons! You can do a rub, you can "brine" the bird, you can place cake tins of water for a "moister cook", you can toss in some wood chips (willow, alder, maple, hickory) that you cause the trash can to be a "smoker", you can inject it, you can stuff oils and herbs under the skin, fill it up with garlic cloves, stand it up a bit higher and stick in 6" of corn silks or even hay (using a bit of water with the latter) and get all sorts of different, but wonderful results.
Of course, if, (incredibly!) your bird is "seriously underdone" you have only to cover it over with the can and stoke up the coals again -- .