Rub roast with salt and pepper. Cut three slits in roast; insert garlic slices. Coat roast with 1/3 cup flour.
Brown roast on all sides in hot oil in a Dutch oven.
Stir together 6 cups water and next 5 ingredients; pour over roast.
Bake, covered, at 350° for 5 hours or until tender.
Remove roast from Dutch oven; keep warm. Whisk together remaining 1 cup flour and remaining 1 cup water. Whisk flour mixture into drippings; cook over medium heat, stirring constantly, until thickened. Serve gravy with roast.