The day before serving, prepare the turkey for brining. Pat dry with paper towels.
Set the neck aside for the stock. Cut off the wing tips and set aside with the neck.
Butcher the turkey into 8 pieces: 2 breasts, 2 legs, 2 thighs, and 2 wings. Set aside the carcass for the stock.
Combine the salt, brown sugar, pepper, and granulated garlic in a small bowl.
Set a wire rack inside a baking sheet. Place the turkey parts skin-side up on the rack and generously sprinkle with the seasoning blend. Refrigerate, uncovered, for at least 2 hours, or overnight.
Make the stock: Preheat the oven to 450˚F (230˚C).
Place the turkey carcass, wing tips, and neck on a baking sheet with the onion, carrots, and celery. Season lightly with salt and drizzle with oil.
Roast for 30-45 minutes, or until the carcass and vegetables are deep brown.
Transfer the roasted vegetables, turkey carcass, and other parts to a large stock pot.
From the still-warm baking sheet from roasting the carcass, pour any rendered fat into a small bowl. Add about 1 cup (240 ml) of water to the pan and scrape off any browned bits from roasting process, then pour into a separate bowl. Reserve for the gravy.
Strain the stock, discarding the solids. The stock will keep for 5 days in the refrigerator or for 3 months in the freezer.
Cover the carcass with cold water. Add the bay leaves and bring to a gentle simmer over medium heat. Continue to simmer (don’t boil!) for 3 hours.
Make the gravy: Heat a medium saucepan over medium heat. Add the turkey fat and flour, stirring to combine. Cook the fat and flour together, stirring constantly, for about 5 minutes. This is a roux--you are cooking out the raw flour taste and deepening the flavor.
Gradually add the stock to the roux, stirring constantly to prevent lumps. Bring to a boil, continuing to stir until thickened. Season with salt and pepper to taste.
Remove the pan from the heat and let cool to room temperature. Store in the refrigerator until ready to warm for serving with the turkey. The gravy will keep in the fridge for up to 5 days, or in the freezer for up to 3 months.
2 hours before you are ready to serve the turkey, preheat the oven to 425°F (220˚C).
Remove the turkey parts from the fridge and drizzle with oil before placing in the hot oven.
Roast for 30 minutes, then rotate the baking sheet to ensure even browning. Reduce the oven temperature to 400˚F (200˚C).
Continue roasting until an instant-read thermometer inserted into the thickest part of breast registers 160°F (70˚C).
Or when the thigh registers 170˚F (77˚C). Start checking after about 20 minutes, removing any parts from the oven as they reach proper temperature so that they don’t overcook.
Once all parts are done, loosely cover with foil and let rest for 5-10 minutes while you warm the gravy.
Add the gravy and sage, if using, to a medium saucepan over low heat and bring to a simmer, stirring occasionally. Season to taste with more salt and pepper, if needed.
Serve the turkey with the gravy and your favorite Thanksgiving dishes.