Prick the pork skin all over with a sharp fork or skewer. Boil about 4 cups (1 L) of water with the vinegar, then ladle it over the pork skin 8–10 times to tighten it and begin rendering the fat. Pat the pork dry thoroughly with paper towels.

Lightly score only the meat side (not the skin). In a small bowl, mix together hoisin sauce, sugar, garlic powder, sea salt, white pepper, and five-spice powder to form a paste. Rub this marinade onto the meat side only.

Sprinkle the 2 teaspoons of salt evenly over the skin. Place the pork uncovered on a rack and air-dry in the refrigerator overnight for best results.

Preheat your air fryer to 250°F (120°C). Wrap the pork belly in an open foil “box,” leaving only the skin exposed. Air fry for 30 minutes to dry the skin and render some fat.

Increase the air fryer temperature to 400°F (200°C). Continue cooking for 30–40 minutes until the skin is blistered, bubbly, and crisp.

If it browns too quickly, reduce the temperature slightly to 375°F (190°C).

Let the pork rest for 20 minutes before slicing into squares. Serve skin-side-up with mustard, hoisin, plum, or ginger-scallion sauce for dipping.