In a 2-qt saucepan, place the pork belly with the onion, garlic cloves, bayleaves, coarsely-grinded salt and soy sauce. Fill with enough water to completely cover or submerge the pork belly.
Using medium heat, bring to a boil. Lower heat to a simmer. Cover and cook for 1-1/2 hours or until the meat is fork-tender. Add water as needed to ensure pork belly is submerged.
Take the pork out of the saucepan and pat dry. Poke holes all over the fatty or skin side of the pork using a fork. (I sometimes simply score it, too.) Salt all over the fatty/skin area. Make sure to use only coarse salt (not the super fine one).
Leave out to dry in the refrigerator overnight or at least 3-4 hours. You want to completely dry out the pork, if possible. The addition of salt on top helps dry it out, too. Brush/scrape off the excess salt (use your hand, a paper towel, or a small brush). If there’s still some remaining moisture in the meat, simply dry it off with a paper towel. Make sure the skin looks dry and matte.
Preheat the air fryer to 350 °F. Place the pork belly, skin side up, in the air fryer basket. Cook for 20-30 minutes or until the skin starts to tighten and some fat has rendered. Increase the temperature to 400 °F, watching closely, until the skin blisters and turns deep golden, about 10-15 minutes more. You need to eyeball this and finish when it's browned and crisp to your liking.
Let it set for 10 minutes to allow the juices to redistribute all over the meat and keep it moist. Slicing the meat right away would not only be messy but all that tasty juice would leave the meat and you don't want that. Your patience, should you wait, would be rewarded with tasty, juicy and tender meat!
Slice into desired thickness (about 1/2 an inch for me usually is good). Serve with some sarsa (Filipino gravy) or a spice soy and vinegar dip. For the sarsa, I simply buy Mang Tomas brand for this because it is the typical lechon sauce and I don’t make it because the bottled variety is quite good. Dip each belly slice into the sauce before eating, if desired.