Season the ribs
Pat ribs dry with paper towels.
Season both sides with garlic salt, onion powder, paprika, salt, pepper, and the 3 tablespoons of mustard, rubbing it in so it coats evenly.
Slow cook the ribs
Pour 1 cup beef bone broth into the crockpot.
Place ribs in the crockpot, meat side up.
Cook on high for 4–5 hours or on low for about 8 hours, until very tender.
Finish under the broiler or grill
Preheat oven to broil on high (or preheat grill).
Carefully remove ribs from the crockpot and place on a foil-lined baking sheet, meat side up.
Brush generously with the browned BBQ sauce.
Broil or grill for 6–7 minutes, or until the sauce is browned, sticky, and slightly charred on the edges.