In a small bowl, combine all the ingredients. Whisk until the sugar dissolves.
Let it sit for 30 minutes, or ideally overnight. Taste and adjust. Add more sugar or water to taste, starting with 1 teaspoon at a time. Note that water will help mellow the acidity of the sauce—use less if you prefer.
Pour into an airtight glass container and store in the refrigerator until needed.
For the pork
Place the water in a pot and bring to a boil.
Add the pork belly and 1 tablespoon of salt. Add the peppercorns, bay leaves, soy sauce, and chili as well. Boil for 30 minutes or until the meat becomes tender.
Remove the meat from the pot and let it cool for a few minutes.
Rub 1 tablespoon of salt over the pork belly, making sure to distribute it evenly over all sections, including the skin.
Begin frying the boiled meat. First, heat the oil in a wok or deep pan.
Carefully place each piece of boiled pork belly into the hot oil and fry until crisp. Turn the meat to fry both sides evenly.
Remove the meat from the pot. If possible, set it on a rack to cool (otherwise, on a plate lined with paper towels). Slice to your desired portion size.
Notes
Be very careful when frying because the oil can splatter as the pork fat 'pops.' Cover the pan about two-thirds with a lid but not completely, otherwise the steam/condensation will have the opposite effect.