Cut the pork belly roughly into large 5cm/2in cubes, leaving the skin on.
Heat the lard in a large pan and throw in the pork bellies. Brown fast and hard, turning occasionally, then transfer to a large ovenproof dish, the pieces should fit fairly snugly without piling on top of each other.
Throw in all the other ingredients, including a generous sprinkling of salt and plenty of black pepper. Transfer the dish to a hot oven of 200C/400F/Gas 6. Check every 8-10 minutes, turning the pieces. After about half an hour the fat rendered from them should be at least half way up the pieces, which will be getting very nicely browned. Turn the oven down to to 160C/325F/Gas 3 and cook the rillons for at least another hour, turning once or twice during that time.
When the skin is tender enough to chew without too much effort, they are done.
Cut each rillons in three or four slices, and sprinkle with a few extra flakes of salt. Serve hot or cold.