Rub roast all over with vinegar mixed with sugar. Rub with salt. Sprinkle roast with flour. Place on rack in roasting pan. Pour a little water in bottom of pan.
Bake uncovered in 500 degree F oven until roast has browned.
Make a sauce from remaining ingredients. Turn oven down to 350 degrees F and baste roast with sauce every 20 minutes, until all sauce has been used.
If sauce gets too thick, add hot water. Cook until done, about 3 hours.

Yields 8 to 10 servings.