1. Using your fingers, carefully loosen the skin over the turkey breast and thighs; try not to tear the skin. Set a large oven roasting bag in a very large bowl. Put the turkey in the bag, cavity end up.
2. In a bowl, mix the bourbon with the orange juice, maple syrup, thyme and 1 1/2 teaspoons each of salt and pepper. Slowly pour the mixture under the turkey skin and press to distribute it evenly over the breast and thighs. Wrap the turkey tightly in the bag and seal with a twist tie. Refrigerate overnight. Bring to room temperature before roasting.
3. Preheat the oven to 325°. Remove the turkey from the bag and set it in a large roasting pan. Pour the marinade into a large measuring cup. Rub 6 tablespoons of the butter under the breast skin and rub the remaining 2 tablespoons over the skin. Tie the turkey legs together with twine.
4. Pour 1/2 cup of the reserved marinade into the roasting pan and roast the turkey for 30 minutes. Baste the turkey with the pan juices and add 1 cup of water to the pan. Roast the turkey for 1 hour longer, basting it every half hour. Add the remaining marinade to the pan. Cover the turkey loosely with aluminum foil and roast for about 2 hours longer, or until an instant-read thermometer inserted in the thickest part of the thigh registers 165°.
5. Carefully transfer the turkey to a carving board, allowing the juices in the cavity to run into the pan. Cover loosely with foil and let rest for 30 minutes.
6. Pour the pan juices into a bowl and skim the fat: reserve 6 tablespoons of the fat. In a large saucepan, mix the fat with the flour to form a paste. In a medium saucepan, warm the Rich Turkey Stock and slowly whisk it into the flour paste. Bring to a boil over moderate heat, whisking constantly. Whisk in the reserved pan juices and simmer over low heat, whisking frequently, until thickened and flavorful, about 25 minutes. Season with salt and pepper and stir in the pecans; transfer to a large gravy boat. Carve the turkey, arrange on a platter and serve with the pecan gravy.