1.Using a sharp knife, score the pork belly skin and fat in a criss-cross pattern, without cutting into the meat. Set aside.
2.Place garlic, ground cloves, caraway seeds, chilli, thyme and some sea salt in a mortar and pestle and crush to a paste. Stir in the olive oil and lemon juice. Rub the marinade over the pork and stand at room temperature for 30 minutes. Preheat the oven to 220°C.
3.Arrange the onion slices in a roasting pan and sit the pork on top. Roast for 30 minutes. Reduce oven temperature to 170°C, then roast for a further 3 hours or until the pork is tender and cooked through, and the skin is crisp. Rest the pork belly, uncovered, for 20 minutes, then cut into slices and serve with salad and mashed potato.