Heat your oven to 140°C/Fan 120°C/Gas 1. Unwrap your pork and pat it dry with kitchen paper. Carefully score the skin on top of the pork with a sharp knife, cutting about ½ cm deep. Generously sprinkle over sea salt and pepper and rub into all of the grooves.
Pop the joint onto a roasting tray and slide into the oven. Roast for about 1 hr 45 mins, or till the meat is soft and tender.
While the belly is cooking, pickle the shallots. Peel and finely slice the shallots and put in a bowl. Season with a little salt and pepper. Zest the lemon and set that aside. Squeeze the juice from half the lemon over the shallots and toss so they’re well coated in the juice. Cover and set aside.
Raise the oven temperature to 220°C/Fan 200°C/Gas 7. Roast the pork for 15 mins, or till the crackling starts to bubble and crisp up. Remove from the oven and leave somewhere warm to rest for about 20 mins.
Roughly chop the parsley and garlic. Mix the parsley, garlic, lemon zest and the juice from the remaining lemon half in a bowl. Season to taste and mix with 1 tbsp olive oil.
Slice the meat, scatter over the pickled shallots and spoon on dollops of the green sauce to serve.