Preheat your oven to 240C/220 Fan/Gas Mark 5 with a baking tray on the middle shelf.
If needed, finely score the pork belly. Dry with a paper towel, rub the skin all over with lemon juice, and then season with salt.
Place in the oven skin side up and roast for 25 minutes until the skin starts to crackle.
Reduce the oven to 160C/150 Fan/Gas Mark 3 and cook for a further 1 1/2 hours until the meat is cooked through but tender. Remove from the oven and make sure to rest for 10 minutes before slicing and serving.