Trim fat from meat. If necessary, cut roast to fit into a 4- to 5-1/2-quart slow cooker. In a large skillet brown meat on all sides in hot oil. Drain off fat.
In the cooker stir together the 1-1/2 cups water, garlic sauce, bouillon granules, and, if desired, sugar. Add sweet pepper, onion, and green beans. Place meat on top of vegetables.
Cover and cook on low-heat setting for 10 to 12 hours or on high-heat setting for 5 to 6 hours.
Transfer meat and vegetables to a serving platter, reserving juices; cover meat with foil to keep warm.
If using low-heat setting, turn to high-heat setting. For sauce, in a small bowl combine cornstarch and the 3 tablespoons cold water; stir into cooking juices in cooker. Cover and cook about 15 minutes more or until sauce is slightly thickened.
Using two forks, separate beef into serving pieces. Serve meat with the sauce, vegetables, and, if desired, hot cooked rice. Makes 6 servings.