If possible, 24 hours in advance, and if not, as far in advance as possible, remove membrane from the back of the ribs. Rub with rib rub, wrap in plastic wrap and refrigerate.
When ready to cook, mix liquid of your choice with the liquid smoke and put in the bottom of the slow cooker. Unwrap ribs, cut into sections to fit in the slow cooker and layer.
Cook on high for 3 1/2 to 4 hours or until ribs are tender. This may vary with slow cookers, so check as it reaches the 3 1/2 hour mark, but don’t check too often or it will slow down the cooking.
Remove Ribs from slow cooker. Place ribs on an aluminum foil-lined sheet pan and slather with sauce. Broil 4 to 5 inches from heat source (set on high) until sauce is bubbly and caramelized. Cut into sections and serve.