Liberally coat the ribs with the dry rub until fully coated.
Place ribs in a 6-quart slow cooker, standing them on their side, leaning against the wall of the slow cooker.
Add liquid smoke to the slow cooker and cook on low for 2 ½ hours then flip the ribs and continue cooking for another 2 hours, for a total of 4 ½ hours.
Ribs are done when the bones can be pulled away from the meat, and the meat cracks when lifted, however, the meat should not fall apart. If the meat is not sufficiently tender yet, just let it cook longer.
Remove ribs from the slow cooker and set broiler on high.
Placing ribs on a rimmed baking sheet, place on middle oven rack under the broiler until a brown crust forms on the meat.
Remove from the broiler and liberally paint with BBQ sauce, then place on the top rack of the oven and broil until BBQ sauce thickens into a jam and threatens to burn.
Remove from oven, let cool briefly, and serve.