Place pork on a baking tray with sides. Using a sharp knife, score skin crossways, about 5mm apart. Pat skin dry with a paper towel. Rub half of the oil over skin and sprinkle with salt flakes. Bake for 1 hour or until skin is crackling, golden and blistered. Reduce oven to 200°C/180°C fan-forced, then bake for a further 30 minutes or until pork is cooked through and skin is crisp. Transfer to a plate, cover loosely with foil and rest for 5 minutes. Thickly slice.
Meanwhile, place blackberries, nectarine, onion, jalapeno, coriander, zest, lime juice and remaining oil in a bowl and toss to combine. Season. Serve pork with salsa and extra lime.
Want to know the secret to perfectly crisp pork crackling? Refrigerate the pork, uncovered, overnight to dry out the skin before roasting.