Spray 5- to 6-quart slow cooker with cooking spray. Remove skin and excess fat from ham. Make cuts in ham about 1 inch apart and 1/4 inch deep in diamond pattern. Place ham in slow cooker.
In small bowl, mix brown sugar, honey, mustard and apple juice. Brush over ham.
Cover; cook on Low heat setting 8 hours or until meat thermometer inserted in center reads 140°F.