Place marinade and lamb into a 1-gallon freezer bag. Spread marinade over all sides of the meat. Seal the bag and refrigerate for 24 hours, the longer the better! When grilling, place the lamb, fat side down. You will get likely get flare-ups, so be prepared with a squirt bottle of water or a couple of cups of water (if using a charcoal grill) to control the flames if needed.