To make this Slow Cooker Shredded Beef gluten-free, confirm that the Worcestershire sauce and beef stock are certified gluten-free or clearly labeled gluten-free. Some Worcestershire sauces, broths, stocks, and seasoning blends may contain gluten-based additives, malt vinegar, wheat, or shared-equipment cross-contact. The chuck roast, onion, sea salt, black pepper, garlic powder, and Italian seasoning are naturally gluten-free, but packaged spices should still be checked carefully. Use clean utensils, cutting boards, measuring tools, and a clean slow cooker insert to prevent cross-contamination.