Score the skin of the pork belly with a very sharp knife in a cross-hatch pattern, being careful only to score down to just before where the skin meets the fat, rather than the fat itself. Bring a large saucepan of water to simmer, and add the bicarbonate of soda. Place the pork belly in the water and poach gently for 5 minutes. Remove it from the water and leave to cool to room temperature.
While the belly is poaching, roast the spices for the salt rub. Place the fennel and chilli flakes in a dry frying pan (skillet) and toast over a high heat for a couple of minutes, until they are fragrant. Watch them so they don’t catch or burn, then transfer to a bowl and leave to cool.
Once the pork belly has cooled, turn it skin-side down and stab it all over the underside with a knife – don’t be shy here, this will help it absorb all that lovely seasoning. Grind the cooled spices in a food processor, spice grinder or pestle and mortar. Add them to the salt and mix.
Rub the underside of the belly all over with the spiced salt rub and pop it in the fridge while you make your stuffing. Heat a tablespoon of olive oil in a non-stick frying pan and add the chopped onion. Season with a pinch of salt and black pepper and sweat together gently for ten minutes, until the onion is soft and fragrant, add the coriander seeds and garlic and cook for a couple more minutes before adding the mince. Cook for a few minutes, until the mince is browned. Set aside and leave to cool.
Transfer the mince and onion mix to a bowl, add the sourdough, pine nuts, orange zest, cherries, herbs and squeeze over the lemon. Season with salt, pepper and freshly grated nutmeg and mix up thoroughly with your hands. Add the beaten egg and incorporate.
Take the pork belly and lie it, skin side down, on the worktop. Form the stuffing into a sausage running all the way down the middle of the belly. Wrap the sides of the belly around the stuffing sausage and tie with butcher’s string. Place stuffing-side down in a baking tray, uncovered, and chill for at least 2 hours, preferably overnight. You want the skin to completely dry out so that it crisps up nicely when you roast it.
To cook the pork, remove it from the fridge and leave it for at least 1 hour to come to room temperature before you cook it. Preheat the oven to 180°C (280°F) and cook the pork for about two hours, turning the tray every 30 minutes or so to ensure it cooks evenly. After two hours, turn the heat up as high as it will go, to 220 and cook for 20 more minutes. Check its core temperature and if the thermometer reads 77 degrees it’s ready. If the skin looks in danger of burning, cover it with foil – but only do this once it has crackled.
Once the pork has cooked, remove it from the oven and leave it to rest for at least 30 minutes.
When you’re ready to carve, clear a big chopping board. Remove the twine from the pork. Take a knife and gently trace the blade underneath the crackled skin, removing it from the fatty bottom of the belly. Cut the meat with a very sharp carving knife; it should fall into nice slices. Place the crackling on the board and use a big knife to chop it up into bite-sized chunks. Serve the pork and stuffing and crackling.