How to Make It
Using a sharp paring knife, poke small slits all over the lamb and insert a garlic slice in each one. Season the meat all over with salt and rub with the harissa and 1/4 cup of the oil, working it into the slits. Set the lamb on a rack in a roasting pan and top with the thyme. Let stand at room temperature for 2 hours or marinate in the refrigerator overnight (bring to room temperature before roasting).
Meanwhile, sprinkle 1 tablespoon of salt and 1 tablespoon of the sugar on a large plate. Arrange the lemon slices on top and sprinkle with 1 tablespoon of salt and the remaining sugar. Drizzle the remaining 1/4 cup of olive oil on top and cover with plastic wrap. Let stand at room temperature for 4 hours or refrigerate overnight. Drain the lemon slices, then rinse and pat dry.
Preheat the oven to 325°. Pour 2 cups of water in the bottom of the roasting pan and roast the lamb for 2 hours, adding water to the pan as it evaporates. Transfer the lamb to a platter and remove the rack. Add the olives, apricots and cured lemon to the pan. Return the lamb to the pan and roast for 30 minutes longer, until an instant-read thermometer inserted in the thickest part of the meat registers 130° to 135°. Stir the olives, apricots and lemon slices occasionally and add a little water if the pan juices get too dry. Transfer the lamb to a cutting board, tent with foil and let stand for 45 minutes.
Scrape the olives, apricots and lemons into a bowl along with any pan juices. Skim off the fat. Slice the lamb and serve with the lemon, olives and apricots.
Harissa is available at specialty food shops or from chefshop.com.