Put the beef in a 6–8-quart slow cooker. Season lightly with salt and ground black pepper.
Whisk the flour and water in a small bowl until smooth, then whisk in the hoisin sauce, soy sauce, tomato paste, chili-garlic sauce, and ginger. Pour into the slow cooker and turn the beef to coat.
Add the star anise.
Cover and cook on low until the beef is tender, about 7–8 hours.
Discard the star anise and transfer the meat to a plate. Shred into bite-size pieces, removing any large pieces of fat. Skim off any excess fat from the liquid in the slow cooker.
Return the meat to the slow cooker and season with salt and pepper.
Cook the noodles as the label directs.
Add the noodles to the slow cooker and mix thoroughly before serving.