01 - Set the oven temperature to 320°F.
02 - Pat the lamb shoulder dry and make small incisions all over with a sharp knife, inserting garlic halves into each slit.
03 - Combine rosemary, thyme, oregano, lemon zest, sea salt, black pepper, and smoked paprika; massage the mixture thoroughly over the lamb, ensuring it presses into the incisions.
04 - Heat olive oil in a large roasting pan over medium-high heat; sear the lamb on all sides until golden brown, about 5 to 7 minutes, then remove and set aside.
05 - Place sliced onions, carrots, and celery evenly in the bottom of the roasting pan and position the lamb shoulder on top.
06 - Carefully pour the white wine and stock around the lamb, avoiding pouring directly over the meat, then cover tightly with foil or a lid.
07 - Cook in the oven for 3.5 to 4 hours, basting once or twice until the meat is tender and easily pulls away from the bone.
08 - Remove the cover and continue roasting for an additional 30 minutes to develop a browned crust.
09 - Tent the lamb with foil and let rest for 15 minutes before carving; serve alongside the roasted vegetables and pan juices.