Remove and discard skin from turkey breast; place turkey in 5- to 6-quart slow cooker.
In small bowl, mix cranberry sauce, soup mix, mustard and salt until well blended; pour over turkey.
Cover; cook on Low setting 6 to 7 hours or until meat thermometer inserted into thickest portion of turkey breast reads 170°F.
About 15 minutes before serving, remove turkey from slow cooker; place on cutting board and cover to keep warm. Place fine strainer over 3-quart saucepan. Carefully pour cooking juices from slow cooker through strainer into saucepan.
In small bowl, blend water and cornstarch until smooth; stir into strained liquid in saucepan. Heat to boiling over medium-high heat, stirring constantly; boil 1 minute.
Cut turkey into slices; arrange on serving platter. Spoon about 1/2 cup gravy over turkey. Serve with remaining gravy.