Venturers spatchcocking turkeys at Winter Rendezvous 2013
To spatchcock your turkey, flip it over and cut out the backbone with a very sharp butcher knife. Throw the backbone, the neck, and the giblets in a pot to make stock.
Flip the bird over and do CPR on it. You should hear an audible crunch and feel it break beneath your hands. Then anoint with oil and season as desired. Place in a pan, all splayed out. Add celery, onions, apples, whatever -- or just roast it plain.
Roast at 450 degrees for an hour with the pan covered in foil. This keeps everything moist. Then remove the foil and continue to roast in an open pan until thigh meat reaches at least 165 degrees internally (an hour to an hour and a half or so, depending on size of bird). Then let rest, so that internal temp rises a bit more, while bird also re-absorbs moisture.
The finished product
Spatchcocked turkey produced at home Thanksgiving 2014
This can be done in any home oven big enough to hold the pan. I've even done them in my 20-qt cast iron dutch oven over an open fire!