Combine bourbon & olive oil in a small container. Brush front & back of ribs. Generously rub front & back of ribs with rub. Wrap plastic wrap or foil. Refrigerate for at least 4 hours, best overnight.
Place slices of onion at the bottom of crock. Place ribs in crock-pot. Try to not let them over lap. Cook on high for 4 hours. Remove ribs from crock-pot and place on a large ovenproof pan. Brush with sauce and broil (low) on the middle rack in the oven until golden brown. Repeat with sauce and broil. Rest ribs, slice & serve.