It's that time of year...
Roast Un-Stuffed Juicy(!) Turkey and Gravy
[n.b. I prefer dressing (in a casserole) to stuffing (in the turkey), for safety and other reasons. And for those who are about to extol the virtues of smoked turkey...I agree. But I am sorely outnumbered by the three women in this family who (A) don't care much for it, and (B) feel that mashed potatoes and lots of good gravy are the best part of Thanksgiving. Gravy is kinda hard to do when smoking a turkey. Younger daughter claims that good gravy is a perfectly acceptable beverage...]
Thaw the turkey the evening before. Remove any pinfeathers, the little bag of giblets from the cavity, and the pop-up thermometer. Get a proper probe thermometer. Dissolve about a cup of salt in a couple gallons of water, in a suitably sized cooler. Add enough ice so that the mixture will remain ice-cold until Thanksgiving day. Immerse the turkey in the salt water and stir a bit. Close the cooler and allow to stand overnight. (Alternative: if the garage is right around freezing, a 5-gallon bucket can be used. Cover with a lid and place in the garage. Just be sure it stays COLD!)
Preheat oven to 400F/200C. Remove turkey from cooler and rinse it thoroughly inside and out, allowing water to drain between rinses. Rinse it again. And again. Be sure to rinse between skin and meat. It's not possible to over-rinse, and if thoroughly rinsed neither the meat nor the gravy will be overly salty. Pat dry with paper towels.
Place a rack in a roasting pan and spray with cooking spray. Place the turkey breast side down* on the rack. Roast for about an hour (for a 12 lb bird, somewhat longer for a larger one). Remove from the oven and CAREFULLY flip the turkey, breast-up. It isn't easy; a couple of silicone oven mitts may help here. Watch out for hot liquid that pools in the cavity! Insert the probe into the thickest part of the breast,
not touching bone.
Turn the temperature down to 325F/165C and return to the oven. Roast until the thermometer registers 165-170F or 74-78C---a little more than two hours for a 12 lb bird, about three hours for a 16 lb. Remove from oven and transfer to a platter. Cover with foil and allow to rest for 30 minutes or so while you make the gravy.
Gravy: Pour off the fat and drippings into a fat-separator cup. Make a roux: for each cup of gravy return about two tablespoons of fat to the roasting pan, and add two tablespoons of flour to the fat. Cook at medium heat and and scrape the bottom of the pan with a wire whisk to get all the good browned bits into the roux. A few minutes of cooking is all that's necessary but if you're careful not to burn the mixture, longer cooking develops more flavor and gives a darker, richer gravy.
When the roux is done, add chicken broth** (a bit less than one cup per cup of gravy) as needed and whisk thoroughly until smooth. Also add the drippings---the stuff below the fat in the fat separator. Bring to a boil, whisking frequently. Turn down to low and simmer for a few minutes until thickened, whisking frequently. If the gravy is too thin, mix equal amounts of the turkey fat and flour, and add this mixture to the gravy, simmering for ten minutes or so until thickened.
Options:
Some cooks advise adding spices, sugar, and whatnot to the brining liquid. I've found that plain old salt by itself is satisfactory.
*It's not absolutely necessary to start with the breast side down. But much of the fat is in the back and thighs. Roasting upside down at first allows some of that fat to melt and soak into the breast. No basting, no rubbing with butter, no nothin'.
**Some cooks simmer the giblets in a cup or so of water, then chop up the meat therein and add broth and meat bits to the gravy. Others (me!) use turkey stock made from last year's carcass and frozen, instead of chicken stock.
Turkey stock: throw leftover parts of the turkey, including the bones, gristle, etc, into a stock pot. Break up the carcass a bit so it fits in the pot. Chop a couple of ribs of celery, a couple of carrots, and an onion, and toss them in. Cover with water and top with lid, bring to a boil, turn down to a simmer and cook for a few hours. Strain through a colander first, dumping everything in the colander. Strain again, lining the colander with cheesecloth. Skim off the fat. Freeze stock and fat separately.
Final Anecdote: We had our neighbors over for roast turkey made this way, many years ago. For the next ten years or so until they moved away, we and a dozen other friends were invited to their place for Thanksgiving...and I was always asked to bring the turkey and gravy. "We'll buy the turkey, but will you
please make it your way??"

We always got compliments on how juicy and tender it was.
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EDIT: Do not roast too long at 400F; if it cooks too much it's very difficult to flip it over without having it rip apart. If you aren't sure, go for 40 minutes instead of an hour.