To make this Crockpot Ham and Potato Casserole gluten free, use a certified gluten-free cream soup substitute, a gluten-free onion soup mix, and a gluten-free stuffing mix. Also confirm that the diced ham and shredded cheddar cheese are free from gluten-containing additives or fillers. Because packaged ingredients can vary by brand, always read labels carefully if preparing this casserole for someone with celiac disease or a strict gluten-free diet.