To make this Slow Cooker Cheesy Kielbasa Hashbrown Casserole gluten free, use a gluten-free condensed cream soup or homemade gluten-free cream sauce in place of the canned cream of chicken soup, since traditional condensed soups often contain gluten. You should also verify that the kielbasa, shredded cheese, onion powder, and any other packaged ingredients are labeled gluten free, as fillers or additives can vary by brand. Frozen hash browns are often naturally gluten free, but it is still a good idea to check the package for cross-contact warnings. If cross-contact is a concern, prepare the casserole in a clean slow cooker insert and use utensils that have not been used with gluten-containing foods.