Using a fork or a knife, poke holes into the skin without piercing the meat.
Place the pork belly skin side down on a flat working surface. Season it with ground black pepper and salt, while massaging the meat.
Add the garlic, onion, spring onion and lemon grass, spread it all over the meat. Do not over-do the stuffing to make it easier to roll.
Tightly roll the pork belly into a log and secure it with kitchen twine by tying up to 5 to 6 knots.
In a small bowl, combine the soy sauce and vegetable oil. Then, rub it into the pork roll. Refrigerate overnight without any cover.
Pre-heat oven to 120° C or 248 °F. Take out the pork belly roll from the fridge and wrap it with aluminum foil.
Using a deep baking tray or roasting pan, combine the remaining stuffings, bay leaves, star anise and 2 cups of water. Place it at the bottom of the oven.
Place the wrapped pork belly roll inside the pre-heated oven and bake it 1 ½ to 2 hours at 120° C or 248 °F.
Remove the aluminum foil wrap and increase the temperature to 180° C or 350 °F. Cook for another 3 hours.
To make it crispier, increase the temperate again to 200° C or 390 °F and cook for another 40 to 60 minutes.
Remove from the oven and let it rest for 30 minutes to an hour before slicing. Serve and enjoy!