Serve food directly from the lined slow cooker. Once your slow cooker cools, remove the liner and throw away for easy clean up.
Here's some "broth math" to help you if don't have any ready-to-serve beef broth on hand. You can use three 10 1/2-ounce cans of condensed beef broth with 2 1/2 soup cans of water or 7 cups of your homemade beef broth. Or add 7 cups of water with 7 beef bouillon cubes or 2 heaping tablespoons of beef bouillon granules.
Vegetarians in your family? Use 4 cans of ready-to-serve vegetable broth instead of the beef broth. The color will not be a rich, deep brown, though, so Golden French Onion Soup may be a more appropriate name!