Using a sharp knife, score the pork rind so that its evenly marked at 1cm intervals.
Combine garlic, ginger, five spice, soy, hoisin, sherry in a ceramic or glass dish big enough to hold the pork belly. Place pork into marinade, skin side up, taking care not to get marinade on the skin side.
Refrigerate, uncovered overnight, allowing pork skin to dry out.
Preheat oven to steam cooking 170°C. Transfer pork belly to a large roasting tray, reserving marinade. Roast for 1 hour 20 minutes or until pork is tender. Brush the skin lightly with oil. Sprinkle with salt. Turn oven up to steam cooking 240°C and roast for 30 minutes or until skin has crackled evenly.
Meanwhile, combine reserved marinade, sugar and ¼ cup water in a small saucepan. Bring to the boil. Simmer, uncovered for 10 minutes.
Serve pork, rested, with marinade sauce, steamed Asian greens and steamed rice.