Rub roast with minced garlic, salt, and pepper. Sprinkle 2 tablespoons flour over entire surface of roast. Place roast, fat side up, on rack in a shallow roasting pan. Insert meat thermometer, if desired.
Bake, uncovered, at 450° for 1 hour. Turn oven off; leave oven door closed. Let roast stand in oven until desired degree of doneness: about 1 1/2 hours or 140° (rare); about 2 hours or 160° (medium).
Transfer roast to a warm serving platter. Let stand 10 minutes before slicing.