We cook a lot of pork - and I always get great crackling!
Sit pork on a bed of a couple of carrots and thickly sliced apple and onion. This keeps the meat off the bottom of the roasting pan.
Turn oven on to preheat a gas mark 8
Rub a little oil over the skin of the meat and give it a good going over with salt and pepper. Salt crystals are best rather than saxa salt, but both will work.
I cook pork at 30-40 mins per lb - so would be about 1 hr 45 to 2 hours for yours.
Put pork in the middle of the oven for 15 mins, then turn heat down to Gas 5 cooking for the rest of the time - do not cover.
take meat out an check its cooked by shoving a knife/skewer into the thickest part. If the juices run clear, great, if not then return it to the oven.
If it is cooked now cut the crackling off with a sharp knife. Stand it up rather than rest it on its back IYSWIM. I've got an oven with the grill staight above it and I put it in there to keep warm whilst I am cooking the rest of the dinner.
Cover the meat in foil, then put a couple of tea towels over it to let it rest and keep it warm.
HTH