Preheat oven to 240C. Using a sharp knife, score pork skin at 1cm intervals and place in a large roasting pan. Drizzle with olive oil, scatter over rosemary and fennel seeds and season to taste with sea salt and freshly ground black pepper. Roast until golden and crackling has formed (40-45 minutes). Reduce heat to 150C and cook until very tender (2½ hours). Remove pork, cover loosely and rest in a warm place (8-10 minutes).
Meanwhile, for salsa verde, combine herbs, garlic, anchovies and capers in a mortar and, using a pestle, pound to a coarse paste, stir in red wine vinegar and olive oil and season to taste. Serve immediately with sliced pork and crusty bread rolls.