1. Bring pork belly to room temperature*. Add the nectar, tomato sauce, Worcestershire, vinegar, sugar, onion powder, oregano, pepper and salt to a mixing bowl and stir until well combined.
2. Slit the pork skin in a diamond pattern and place it in the slow cooker skin side down. Pour the sauce mixture over the pork and cover. Cook on high for 3 hours or low for 6 hours. Turn the pork over and cook on high for another hour or low for 2 hours, or until the pork is tender.
3. Carefully transfer the pork to a serving platter. Slice and spoon the pan juices over the top to serve.