For a deeper flavor, sear the chuck roast on all sides in a hot pan before adding it to the slow cooker. Add other vegetables like parsnips, turnips, or celery for added complexity. If you prefer a thicker gravy, increase the amount of flour in the slurry. Fresh rosemary can be substituted, use 1 tablespoon chopped fresh rosemary. The cooking sherry can be substituted with red wine or beef broth. Adjust salt and pepper to your taste after thickening the sauce.