DH has a great recipe (at least I thnk so).
Start with an aluminum roasting pan (the kind you can buy in the grocery store) big enough to fit the slab or ribs (cut into 2 pieces if necessary) and at least a gallon of bottled BBQ sauce (flavors up to you). Then season to taste. We usually use a little vinegar (enough to rinse out the BBQ sauce bottle without being overpowering), a LOT of garlic, onion powder, cayenne, pepper, a little salt, and some mint (sounds strange, but really brings out the rest of the flavors).
Marinade overnight. About 4-5 hours before you want to eat, preheat grill. Sear the ribs on the grill, then place back in the sauce. Reduce heat to low, then put the pan on the grill. Turn/baste the ribs every hour or so. Falling off the bone delicious!