Preheat oven to 180°C. Place the lamb in a large roasting pan. Drizzle with oil and sprinkle with salt and paprika. Use a small, sharp knife to cut small slits, about 2cm deep, over the surface of the lamb. Place a slice of garlic, rosemary and oregano in each slit.
Drizzle chicken stock and wine around the lamb and cover with foil. Cook in preheated oven for 1 hour. Remove from oven and spoon pan juices over the lamb. Arrange the onion, potato, lemon and olives around the lamb. Reduce heat to 150°C. Cover and roast for a further 1 hour. Remove the foil and roast for a further 30 minutes or until lamb is golden brown and very tender. Remove from oven and cover with foil. Set aside for 15 minutes to rest.
Thickly slice the lamb and arrange on serving plates with onion, potato, lemon and olives. Drizzle with pan juices to serve.