In 4 to 6-quart slow cooker, combine onion and apples. In small bowl, combine honey, mustard, coriander and salt; mix well. Spread on all sides of pork roast. Place pork over onion and apples.
Cover; cook on Low setting 7 to 8 hours.
Remove pork from slow cooker; place on serving platter. Cover with foil.
In small saucepan, blend water and cornstarch until smooth. Add apple mixture and juices from slow cooker; mix well. Cook over medium heat until mixture boils, stirring occasionally. Cut pork into slices. Serve pork with sauce.