Mix the salt, sugar, paprika, garlic powder, cumin, dry mustard and cayenne pepper in a container with lid. Close lid and shake
Trim the sparerib slab by removing the membrane from the bone side and trim any excessive fat from the meat side that cannot melt when grilled
Coat a thin layer of mustard on the ribs. This helps glue the dry rub to the meat
Sprinklel a layer of the dry rub over the whole slab, 1 hour before cooking to absorb flavors. Be generous with the rub, but don't use all the rub mix if you don't believe it needs it.
Place the ribs, bone side down, in a 275°F (135°C) smoker
After 2 hours, check the ribs. If the ribs look too dry, spray with water or apple cider.
Check the smoker temperature and add more charcoal, carbon, or briquettes, if needed to maintain the 275° F (135°C) temperature.
After 1 more hour wrap the ribs in aluminum foil, adding on the bottom 1/4 cup of apple cider/juice. Wrap and put back in the smoker and elevate the temperature to 300°F (149° C) until the ribs are tender. Approximate 2 more hours, checking for tenderness
Remove from heat, let rest for 5 minutes, brush with your favorite bbq sauce and enjoy!