Place marinade of choice in a large baking dish, and marinate the boned lamb in the refrigerator for 12 to 24 hours. Let it come to room temperature, then take it out of the marinade and wipe it dry. (If the surface is damp, it won't sear properly.) Prepare the grill. The coals should be red-hot with a coating of ash. Pare a piece of fat from the meat, impale it on a long fork, and rub it over the grill. Place the flattened lamb on the grill and sear it for 2 or 3 minutes on each side. Raise the grill 4 or 5 inches, using bricks if necessary to get the desired height. Continue to cook the meat for 5 to 8 minutes more on each side, basting with the marinade. Judge for doneness as for steak – the lamb should be nice and pink inside. This lamb can also be broiled; broil on a preheated pan 4 to 8 inches from heat – just as if using a grill.