1. Pat the pork belly thoroughly dry with paper towels. Score the skin deeply with a sharp knife, making parallel lines about 1/2 inch apart, being careful not to cut into the meat layer. 2. Flip the pork belly to the meat side. Mix Chinese five-spice powder, white pepper, sugar, and Shaoxing wine (if using) in a small bowl. Rub this mixture evenly over the meat side, avoiding the skin. 3. Flip the pork belly back to the skin side. Pierce the skin all over with a meat tenderizer tool or a fork. The more holes, the crispier the skin will be. 4. Brush the skin with white vinegar, then generously rub the coarse sea salt over the entire skin surface, pressing it into the scores and holes. 5. Place the pork belly, skin-side up, uncovered in the refrigerator for at least 8 hours, or preferably 24 hours, to allow the skin to dry completely. This is crucial for crackling. 6. Preheat oven to 400°F (200°C). Remove pork belly from fridge. Scrape off the excess coarse salt from the skin (it will have absorbed moisture and formed a crust). 7. Place the pork belly on a wire rack set over a baking sheet (to catch drippings). Roast in the preheated oven for 30 minutes, or until the skin starts to puff up and blister. 8. Reduce oven temperature to 325°F (160°C). Continue roasting for another 60-90 minutes, or until the internal temperature of the meat reaches 160°F (71°C) and the skin is golden brown and crispy. 9. If the skin isn't uniformly crispy, you can use the broiler for a few minutes, watching *very* closely to prevent burning. Move pork belly to an upper rack if using broiler. 10. Let the pork belly rest for 15-20 minutes before carving into thick slices. Serve immediately with your favorite dipping sauce.