In a large skillet brown meat, half at a time, in hot oil. Drain off fat. In a 3-1/2-to 5-quart slow cooker place mushrooms and onion. Add meat. In a bowl combine undrained tomatoes, the 1 cup water, the dried marjoram and thyme (if using), bouillon granules, salt, and pepper. Pour over all.
Cover and cook on low-heat setting for 8 to 10 hours or on high-heat setting for 4 to 5 hours.
If using low-heat setting, turn to high-heat setting. In a bowl stir together the 1/3 cup water and the flour. Stir flour mixture into pork mixture in cooker. Cover and cook on high-heat setting for 15 to 20 minutes or until thickened. If using, stir in fresh marjoram and thyme. If desired, serve over hot cooked rice. Makes 4 servings.