01 - Preheat the oven to 320°F.
02 - Pat the lamb shoulder dry and make small incisions all over the meat; insert garlic halves into these incisions.
03 - Combine rosemary, thyme, oregano, lemon zest, salt, pepper, and smoked paprika; rub evenly over the lamb, pressing the mixture into the incisions.
04 - Heat olive oil in a large roasting pan over medium-high heat and sear the lamb on all sides until golden brown, about 5 to 7 minutes; remove and set aside.
05 - Scatter onions, carrots, and celery in the bottom of the roasting pan, then place the lamb shoulder on top.
06 - Pour wine and stock around (not over) the lamb; cover tightly with foil or a lid.
07 - Roast for 3.5 to 4 hours, basting once or twice, until the meat is extremely tender and pulls away from the bone.
08 - Uncover and roast for the final 30 minutes to develop a browned crust.
09 - Rest the lamb, tented with foil, for 15 minutes before carving. Serve with the roasted vegetables and pan juices.