Heat the oven to 160C/fan 140C/gas mark 4. Dry the belly slices with kitchen paper, then season with salt and pepper. Mix together the ingredients for the sauce and toss the slices in the sauce in a roasting tin. Cover tightly with foil and roast for 1hr 30 mins, until completely tender.
Remove the foil and turn the grill to its highest setting. Grill the meat for 3-4 mins, turning it halfway and brushing over the sauce from the tin, until the sauce is thick and sticky and the slices are charred. Alternatively, put the braised slices on the barbecue and baste in the sauce from the roasting pan as they sizzle away. Serve in buns with coleslaw.