01 - Preheat the oven to 320°F.
02 - Pat the lamb shoulder dry. Make small incisions across the meat and insert the garlic halves into these slits.
03 - In a bowl, combine rosemary, thyme, oregano, lemon zest, sea salt, black pepper, and smoked paprika. Rub this mixture thoroughly over the lamb, pressing into the incisions.
04 - Heat olive oil in a large roasting pan over medium-high heat. Sear the lamb on all sides until a golden crust forms, about 5 to 7 minutes. Remove the lamb and set aside.
05 - Spread onions, carrots, and celery evenly across the bottom of the roasting pan. Position the lamb shoulder on top of the vegetables.
06 - Pour white wine and stock around the lamb, avoiding pouring directly over the meat. Cover the pan tightly with a lid or heavy-duty foil.
07 - Place the pan in the oven and roast for 3.5 to 4 hours, occasionally basting once or twice, until the meat is tender and easily separates from the bone.
08 - Remove the cover and continue roasting uncovered for the last 30 minutes to brown the lamb.
09 - Let the lamb rest tented with foil for 15 minutes before carving. Serve alongside the roasted vegetables and pan juices.