Stir together the following ingredients to form the marinade:
½ tbsp salt
Score the flesh part (not the skin) of the pork belly lightly in diagonal lines and rub in the marinade well. Place the joint in a foil-lined roasting tin, marinated side down so it can sit and absorb the flavours.
Score the skin part this time, using a sharp knife and being as thorough as possible. Rub in lots of salt all over, deep into each cut.
Leave the joint uncovered overnight to dry completely. Room temperature is fine in cold climates like London, but you should refrigerate the meat if it's hot where you are.
When ready to cook, lift the joint up and place a wire rack underneath to enable fat to drip off into the pan. Pat dry if there is any moisture left on the skin and bake in the middle of a 200C fan-assisted oven.
After 20 mins, remove and stab the skin all over as much as possible using two forks, one in each hand (I find this much steadier and faster than just using one hand). Drizzle the skin all over with a few tablespoons of rice vinegar.
Return the pan to the oven and switch it to grill setting (upper heat only) at very high heat, about 250C. You will see the crackling start to bubble and pop wherever you poked with a fork. Grill for a further 30 mins, opening the oven door intermittently to let smoke escape, until the skin gets slightly burnt and charred. Don't worry about the blackened bits- it can be removed easily and is essential to ensure the crackling achieves the correct crispiness.
Once cooked, remove from the oven, scrape off any burnt parts with a serrated knife and leave to rest 15 mins before chopping.
Listen to the satisfying crunch as you cut your siew yoke into chunks.
Save the cleaning up for later and devour with hot steaming rice.