Spray 4- to 5-quart slow cooker with cooking spray. Spread mustard on 1 side of each pork chop; sprinkle with dried thyme. Place pork in cooker. Pour gravy over pork.
Cover; cook on Low heat setting 6 to 7 hours.
Remove pork to platter; keep warm. Strain cooking liquid into 2-quart saucepan; heat to boiling. Meanwhile, in small bowl, stir water, flour and salt until well blended; stir into boiling liquid. Boil and stir 1 minute. Serve gravy with pork. Garnish with fresh thyme.