1. Preheat oven to 325°.
2. Remove giblets and neck from turkey; discard liver. Reserve turkey neck and giblets. Pat turkey dry with paper towels; trim and discard excess fat. Starting at neck cavity, loosen the skin from breast and drumsticks by inserting fingers, gently pushing between the skin and meat.
3. Combine 2 tablespoons sage, olive oil, butter, 1 teaspoon salt, and 1/4 teaspoon black pepper. Rub sage mixture under the loosened skin and over breasts and drumsticks. Squeeze juice from 1 half of lemon over turkey; place remaining lemon half in cavity. Tie legs together with kitchen string. Place reserved giblets, neck, garlic, carrots, celery, onion, and bay leaf in the bottom of a large roasting pan. Add 1 cup stock and 2 cups water to pan. Place roasting rack in pan. Arrange turkey, breast side up, on roasting rack. Bake turkey at 325° for 1 hour and 20 minutes, rotating pan every 30 minutes. Increase oven temperature to 425° (do not remove turkey from oven). Bake turkey an additional 30 minutes or until a thermometer inserted into meaty part of thigh registers 165°. Remove turkey from pan; place on a cutting board. Let stand for 30 minutes. Carve turkey; discard skin.
4. Place a large zip-top plastic bag inside a 4-cup glass measure. Strain pan drippings through a colander into bag; discard solids. Let drippings stand 10 minutes. Seal bag; snip off 1 bottom corner of bag. Drain pan drippings into a medium saucepan, stopping before fat layer reaches the opening. Add remaining 1 tablespoon sage, remaining 1/4 teaspoon salt, remaining 1/4 teaspoon black pepper, 1 1/2 cups chicken stock, and wine to drippings in pan; bring to a boil. Cook for 15 minutes or until reduced to 2 1/2 cups. Combine flour and remaining 1/2 cup chicken stock in a small bowl, stirring with a whisk until smooth. Stir flour mixture into stock mixture in pan; bring to a boil. Boil 1 minute or until slightly thick, stirring gravy constantly. Serve gravy with turkey.