Rinse and pat the dry the ribs with a paper towel. Remove any silver skin on the top side of the ribs and the thin membrane from the underside of the ribs.
Split the racks in half and place them on a baking sheet.Rub the mustard onto the tops and sides of the ribs. Season the ribs with sea salt and cracked black pepper.
Wrap the half rack of ribs in foil. Seal the edges of the foil, making sealed packets. Place the ribs in the 275-degree preheated oven on a rack in the center of the oven.