Working in batches, sear ribs on all sides in the hot skillet. You want the outsides of the ribs to brown. Two to three minutes per side should be plenty.
Transfer ribs to slow cooker.
Use 1/2 cup beef broth to deglaze the pan, and pour this over the ribs.
Layer chopped onion over ribs.
Crush the Italian seasoning in your palms, and sprinkle over the ribs.
Pour beef broth over ribs. Your slow cooker should be nearly full, and the ribs should be almost (or completely) covered with broth.