Brush the lamb with extra virgin olive oil and season heavily, all over, including the underside, with sea salt and coarse black pepper.
Lay the lamb on a trivet of onions, garlic, fresh thyme, bay leaves, and rosemary, and extra virgin olive oil.
Preheat the oven to 200c fan / 220c.
Roast the lamb for 30 mins.
Take the lamb out, add 500ml chicken stock to the tray, cover tightly with foil, and reduce the heat to 160c fan / 180c.
Cook the lamb for 4 hours (do not baste or take the tray out of the oven).
Remove the foil and cook the lamb for a final 30 mins uncovered.
Take the lamb out and rest it, covered with foil, for 30 mins before serving.
