Rub pork roast with salt and pepper. Make tiny slits in the meat and insert slivers of garlic. Place roast in broiler pan and broil 15-20 minutes to remove excess fat.
Put 1 sliced onion in the bottom of the crockpot. Add browned pork roast and remaining onion and other ingredients. Cover and cook on Low until done, about 10 hours.
To thicken gravy: Remove roast to serving platter. Blend 2 tb cornstarch with 2 tb water to form a smooth paste. Set crockpot on High and pour in the paste. Stir well and let it come to a boil, about 15 minutes, or until thickened.