Remove the membrane from the back of the ribs if present. Use a knife to loosen, then peel off using a paper towel.
Rub olive oil over both sides of the ribs and coat them generously with the dry rub. Massage seasoning into the meat for maximum flavor.
If necessary, cut ribs into 2–3 rib sections to fit them into the crockpot. Layer the ribs, standing on their sides or stacking.
Mix barbecue sauce and apple cider vinegar in a small bowl. Pour 1 cup of the mixture over the ribs, reserving the rest. Cover and cook on Low for 7–8 hours or High for 4–5 hours, until tender.
Preheat the broiler to high. Carefully remove ribs from the crockpot and place them on a foil-lined baking sheet.
Brush the ribs generously with the reserved barbecue sauce. Broil for 3–5 minutes, until the sauce caramelizes and becomes sticky. Watch closely to avoid burning.
Garnish with fresh parsley or green onions, if desired. Serve hot with extra barbecue sauce on the side. Pair with coleslaw, mashed potatoes, or cornbread for the ultimate barbecue meal.