Remove giblets and neck from turkey; discard. Rinse turkey thoroughly with cold water; pat dry. Combine orange juice, water, 1/2 cup bourbon, and molasses in a 2-gallon heavy-duty ziptop plastic bag; add turkey. Seal and marinate in refrigerator 4 to 24 hours turning bag occasionally. Remove turkey from bag, reserving marinade.
Preheat oven to 350 degrees.
Tie ends of legs with cord. Lift wing tip up and over back and tuck under bird. Sprinkle 1/2 teaspoon salt into body cavity. Stuff cavity with oranges. Place turkey on a broiler pan coated with cooking spray or on a rack set in a shallow pan. Insert meat thermometer into meaty part of thigh, making sure not to touch bone. Bake at 350 degrees for 3 hours or until thermometer registers 180 degrees. (Cover loosely with foil if it gets too brown.) Remove turkey from oven. Cover loosely with foil; let stand at least 10 minutes before carving. Discard oranges.
Pour reserved marinade into saucepan; bring to a boil. Skim foam from mixture with a slotted spoon; discard. Reduce heat to medium; cook until reduced to 3 1/2 cups (about 15 minutes). Combine 1/4 cup bourbon and flour in a small bowl, stirring well with a whisk. Add to reduced marinade; bring to a boil and cook 1 minute, stirring constantly. Stir in 1/4 teaspoon salt. Serve sauce with turkey. Garnish with orange slices and parsley sprigs if desired.