1. Preheat the oven to 200C fan-forced or 220C conventional.
2. Place the pork in a roasting dish,skin side down - along with the garlic,liquorice root,star anise,brown sugar and soy - and pour over enough boiling water to cover it. Bring to a simmer on the stovetop,then place in the oven,roast for 30 minutes,turn the belly over to skin side up and roast for another 30 minutes.
3. Remove the dish and lift the pork out of the liquid. Using a sharp knife,score the skin in a crisscross pattern and lay on a tray lined with baking paper. Cover with another sheet of paper and another tray,weigh down andrefrigerate overnight.
4. When ready to cook,preheat the oven to 200C fan-forced or 220C conventional.
5. Place the sliced onions in the bottom of a heavy roasting dish,rub the pork with oil and salt and roast,skin side up,for an hour. The skin should have crackled but,if necessary,turn on the grill to finish the crackle. Rest for five minutes before cutting into squares or slices.
6. Mix the Sriracha and mayonnaise together and serve alongside the pork and slaw (below).
Serve withKaren Martini's Vietnamese mint and chilli slaw and pickled beets.