1. Build a charcoal fire for indirect cooking by situating the coals on only one side of the grill, leaving the other side empty. Preheat the grill to 250°F.
2. For the dry rub: In a small bowl, combine the salt, brown sugar, chili powder, coffee, cocoa, black pepper, garlic powder, onion powder, ancho chile pepper, coriander and turmeric.
3. Remove the membrane from the back of the ribs. Generously apply the dry rub onto the front and back of the ribs. Gently pat to ensure that the rub adheres.
4. Put the slabs meat side up over indirect heat, away from the coals, close the lid, and cook until the ribs are tender, about 3 hours 30 minutes.
5. Remove the ribs from the grill and let them rest uncovered for 5 minutes. Slice the ribs between the bones and serve.