Turkey stock is a great way to add a little oomph to your pan gravy. It's a flavorful base that's a snap to make and adds complex flavor to many other dishes as well. Once you try it, you'll never go back to using just water again.
*Note: Many butchers or butcher departments of some grocery store chains may already sell turkey legs, thighs, and wings. If yours doesn't, you can always purchase a small 8- to 10-pound turkey and have the butcher cut it up, removing the wings, legs, thighs, back, and neck for you to use in this stock. You can roast the breast separately (it will cook in half the time unencumbered by its legs and thighs) and refrigerate or freeze the meat for after Thanksgiving sandwiches.
Preheat the oven to 450 degrees.
Line a rimmed baking sheet with foil. Arrange the turkey parts (you can use the gizzards as well if you like the flavor), onions, and garlic halves on the tray in 1 layer. Liberally drizzle with the olive oil and, using your fingers, spread the oil to coat everything. Roast until the meat and vegetables are very brown, about 1 hour.
Transfer the contents of the baking sheet (drippings, liquid, and all) to a large stockpot. Add the remaining vegetables to the pot. Add enough water to thoroughly cover all the meat by about 1 inch. Bring the liquid to a boil, then reduce the heat and simmer for 1 hour.
Remove as many of the meat solids and bones as possible from the pot with a slotted spoon, then strain the liquid through a fine-meshed sieve (lined with cheesecloth if you want a clearer broth), and discard the remaining solids.
Stock should be cooled completely to 70 degrees or lower before being transferred into plastic containers and refrigerated. It can be stored in the refrigerator in airtight containers for up to 1 week, or frozen for up to 3 months. (If you do freeze stock, remember to leave enough room in the container for the liquid to expand while freezing or else you will end up with cracked containers and freezer-burned stock.)