Ask your butcher to take out the bone but give it to you to use in the pan to help make the gravy.
Method
Stab the joint several times over with the tip of a small sharp knife and insert one ½ clove of garlic per incision. Also stick in a little sprig of rosemary per incision.
Place the shoulder on the lamb bones with the 2 carrots cut in half, drizzle over the olive oil and season with sea salt and pepper.
Place in the oven at 160C/Gas2 for 4-5 hours, covering with a sheet of foil for the first 3 hours. With one hour to go, throw in the peeled shallots and remove the foil.
When the lamb and shallots are cooked, remove everything from the tray and allow to rest.
Add the tomato purée and flour to the cooking tray and place back on the stove to cook slightly. Then add the stock and bring to the boil. Strain through a sieve into a clean pan and bring back to the boil.
Carve the lamb onto a serving dish, place the shallots around. Serve with green vegetables, roast potatoes and gravy.
Recipe by appetite magazine at https://www.appetitemag.co.uk/slow-cooked-shoulder-of-lamb/