Think of a good gravy as the final chef's kiss on a fabulous Thanksgiving dinner. This is the version Martha likes to serve with her smoked bird.
Preheat oven to 425°F. Arrange turkey neck, giblets, and pieces in a single layer (or close to it) in a roasting pan or large skillet. Roast until golden brown all over, about 1 hour, 30 minutes. Transfer to a small stockpot. Add carrots, onion, celery, bay leaf, and stock to cover. Bring to a boil over medium-high heat, skimming and discarding any foam that rises to surface. Reduce heat to low and simmer until reduced to about 3 1/2 cups, 30 to 45 minutes.
Strain, discarding all solids but neck and giblets. Let broth stand 10 minutes, then skim fat from surface and discard. Remove meat from neck and shred. Cut up giblets.
Meanwhile, place roasting pan over medium heat. Add wine and cook, scraping up browned bits, until liquid has almost evaporated and all the bits have come up from bottom of pan, 3 to 5 minutes.
Add 2 1/2 cups strained broth, shredded neck meat, and chopped giblets to pan; bring to a boil, then reduce heat to low and simmer 10 minutes. In a small, tightly covered jar, shake remaining strained broth and flour to combine, then whisk mixture into the simmering broth. Return to a boil, then reduce heat to low and simmer until thickened, 1 minute. Season with 1 1/2 teaspoons salt and 1/2 teaspoon pepper. Serve as is, or strain (you should have about 2 cups strained, more like 3 unstrained).