Spray 3- to 4-quart slow cooker with cooking spray. Place beef in cooker. In small bowl, mix dry soup mix and broth; pour over beef.
Cover; cook on Low heat setting 8 to 10 hours.
Skim fat from liquid in cooker. Remove beef from cooker; place on cutting board. Cut beef across grain into thin slices or shred beef.
To serve, cut each baguette in half horizontally. Fill baguettes with beef; cut crosswise in half. Serve with broth for dipping. Beef mixture will hold on Low heat setting up to 2 hours; stir occasionally.