; 03 Cut each potato crosswise into thin slices, stopping about three-quarters of the way through the potato so the slices remain attached at the bottom. Roast for 1 hr 30 mins, basting the potatoes and shaking the tin occasionally, until the lamb is dark brown and the potatoes are crisp and golden. 01 Place the leg of lamb on a premium grilling rack. Instructions. 02 In a small bowl combine all the marinade ingredients and mix well. Season the leg generously on all sides with salt and pepper. Nestle the lamb in the middle of the tin, pushing the potatoes to the outside, then rub the lamb with the rest of the oil and the lemon juice and season generously.