The best way to produce meltingly tender meat from a joint such as lamb shoulder or belly pork, in my oven, is to pot-roast it. The heat inside a heavy casserole is lower than the oven temperature at the lowest setting (about 130C). See also Foil and slow roasting.
You can get good pork crackling, too. Following a long quest for crackling perfection (I have written numerous entries on the subject), I have so far yet to record a failure after rubbing vinegar over the skin. The theory behind this technique is that the acid helps to break down the collagen, the protein that provides the skin's rubbery texture.
I had a 1.2kg piece of belly pork, which serves four people easily.
Try to leave the pork uncovered for a while, with salt sprinkled on the skin. When you’re ready to cook the joint, use a paper towel to wipe off the moisture that the salt will have drawn out. Smear a little oil on the meaty underside. Smear a tbsp of vinegar on the skin. Season all over with salt and pepper. You may like to use fennel, too.
Put the belly pork into a grill pan, and grill the skin until it starts to brown.
Slice two onions into rings, mix them with a little oil, and put them into a heavy casserole. Lay the bellow pork on top, put on the lid, and cook at the lowest possible heat at the bottom of the oven, for five to six hours.
Slice off the skin, return the pork to the casserole, and cover to keep warm. Turn the oven to its highest setting, put the skin in a dish or on a baking sheet, and bake until it is crunchy.
The meat from the joint should be tender enough to cut with a spoon.