Preheat oven to 160°C.
Arrange the garlic over the base of a baking dish. Rub the olive oil all over the pork belly and rub the salt into the skin.
Place skin-side down on top of the garlic and cook for 3 hours.
Increase the heat to 180°C. Turn over the pork, add the sage and cook for a further 30 minutes or until the skin is golden and crunchy.