Spray slow cooker insert with non-stick cooking spray. Arrange ribs in slow cooker insert, wrapping them around the inside of the insert or by cutting them in thirds or halves if necessary. Pour BBQ sauce over ribs, reserving 1/2 cup in an airtight container in the refrigerator for later use.
Cook over low for 6 hours. Spoon remaining BBQ sauce over ribs for serving, if desired. If not, serve on the side.