01 - Preheat the oven to 400°F. Pat the lamb leg completely dry with paper towels to ensure proper browning.
02 - In a small bowl, combine olive oil, chopped rosemary, thyme, lemon zest, salt, and pepper. Mix thoroughly to form a paste.
03 - Using a sharp knife, cut deep slits all over the lamb. Push halved garlic cloves into each slit to infuse flavor throughout.
04 - Rub the herb mixture evenly over the entire surface of the lamb, pressing firmly to adhere.
05 - Arrange onion slices, carrot chunks, and halved garlic bulb in a large roasting pan to create a vegetable bed.
06 - Place the seasoned lamb leg directly on top of the vegetables. Pour wine or stock into the bottom of the pan.
07 - Roast at 400°F for 20 minutes to develop a caramelized exterior crust.
08 - Reduce oven temperature to 350°F. Continue roasting for 1 hour 10 minutes for medium-rare (internal temperature 140°F), basting every 20 minutes with pan juices.
09 - Remove lamb from oven and tent loosely with aluminum foil. Let rest for 15-20 minutes to allow juices to redistribute throughout the meat.
10 - Carve the lamb against the grain into thin slices. Serve with roasted vegetables and drizzle with pan juices.