Remove all the usable turkey meat from the turkey carcass.
Place the turkey carcass, neck (not cooked), leftover skin, bones and drippings, into a large stock pot (8-12 quart depending on the size of the turkey), and cover with COLD water by an inch.
Add thickly sliced onion, some chopped carrots, celery (including tops), parsley, thyme, a bay leaf, and some peppercorns to the pot.
Bring to a boil, reduce to a simmer, skim foam.
Add salt and pepper (to taste) to the pot.
Cook for at least 4 hours, partially uncovered, occasionally skimming off any foam that comes to the surface.
Strain the stock and let cool. Place in storage containers.