01 - Preheat the oven to 300°F.
02 - Pat the leg of lamb dry with paper towels. Using a sharp knife, make small incisions all over the lamb and insert garlic slices into the cuts.
03 - In a small bowl, combine lemon zest, lemon juice, rosemary, thyme, salt, pepper, and olive oil. Rub this mixture all over the lamb, ensuring it is well coated.
04 - Arrange the onion slices and carrot chunks in the bottom of a large roasting pan. Place the lamb on top of the vegetables.
05 - Pour the white wine or chicken broth into the bottom of the pan.
06 - Cover the pan tightly with foil and roast for 2.5 hours.
07 - Remove the foil, increase the oven temperature to 400°F, and roast uncovered for an additional 30 minutes until the lamb is golden and the exterior is crisp.
08 - Remove from the oven and let the lamb rest, loosely covered with foil, for 15 minutes before carving. Serve with the roasted vegetables and pan juices.