Slow Cooker Hot Beef Sandwiches Au Jus My roast beef turned out very dry. My Crock Pot cooks very fast so I took the meat out after 4 1/2 hours. I let it cool and sliced it thin. After slicing I put it in the refrigerator with enough Au jus to cover. The remaining Au Jus I refrigerated so I could skim off the fat and reheat for the sandwiches. After sitting in the au jus the meat got juicy and the sandwiches were a great hit for the Super Bowl.