Return the lamb to the pan and stir. Add the thyme, bay leaves, and the garlic cloves to the meat and vegetables, along with the shoulder bone(s), and enough water to cover. When the water comes to a boil, remove it from the heat, cover, and place the pot in the center of the oven. Bake until the lamb and the vegetables are tender through. Remove it from the oven and when it is cool enough to handle, go through the pieces of lamb with your fingers, shredding them.