Cut your pork belly in half, you want it about a 8x6 inch slab.
4 lbs skin on pork belly
Make vertical slits along the meat side about ½ inch deep. Season ONLY the meat side with five spice, brown sugar, garlic powder, and salt.
1 tsp five spice powder, 2 tsp brown sugar, 2 tsp garlic powder, 1 tsp salt
Let it sit in the fridge over a wire rack with the skin side up overnight. This will allow the skin to dry up.
Next day, create a tin foil boat that tightly wraps around the meat side of the pork belly. This just prevents the meat from burning.
Add enough salt to fully cover the skin. You want to use kosher salt or something more coarse so that it doesn't actually penetrate the skin. Sea salt is too fine.
2 tbsp oil or white vinegar, ½ cup kosher salt
Place in an oven at 300F for 1.5 hours. The meat will cook and shrink, causing it to get taller. The reason I use the oven and not the air fryer in this step is because the air fryer fan is very intense and will blow away all the salt.
Remove all the salt from the skin. Brush with a layer of oil.
Place into an air fryer at 450F for 20 minutes or until the skin is crispy and light. If you do not have an air fryer, place it into your oven at the convection bake on highest temperature.
Cut into it and serve with a mixture of water and hoisin sauce. I use a 1:1 ratio.