01 - Set oven temperature to 400°F.
02 - Pat the leg of lamb dry. Make small incisions all over and insert garlic slices into the cuts.
03 - In a small bowl, combine rosemary, thyme, sea salt, black pepper, olive oil, lemon zest, and lemon juice. Rub mixture thoroughly over the lamb.
04 - Lay onion, carrot, and celery chunks evenly in a large roasting pan to create a vegetable bed.
05 - Place the lamb atop the vegetable bed. Pour white wine or lamb stock into the pan.
06 - Roast lamb in the oven for 1 hour and 30 minutes for medium-rare doneness, basting occasionally. For medium doneness, extend cooking time by an additional 15 minutes.
07 - Remove lamb from oven, loosely cover with foil, and rest for 15 to 20 minutes prior to slicing.