Spread out the rack of ribs in a single layer in the bottom of a large roasting pan. Slather on half of the barbecue sauce. Cover and bake until the meat is tender and falling off the bone (195°F/90°C), about 3½ hours.
Remove the lid. Add more barbecue sauce and, optionally, broil or grill for 5 to 10 minutes, depending on how close the meat is to the heat source, to caramelize the sauce.
Because of the low baking temperature for these ribs, they're rather forgiving if you leave them in a little longer than planned.
If you take them out of the oven a little earlier, your meat will likely be cooked but perhaps not as tender and falling off the bone as it could be.
Reheat leftovers in a covered dish with some extra sauce for about half an hour at a low temperature (300°F/150°C).