Yes! To make this corned beef brisket in a slow cooker, spread out the cut onion and garlic cloves in the bottom of a Crockpot (or any other slow cooker). Place flat cut brisket on top of the onions, fat cap up, and add the seasoning mix. Pour in beef stock and make sure that it just covers the brisket. The size of the brisket does effect the coverage with broth. So if using a wide slow cooker, place brisket right on the bottom with onions around it. Close the lid and let it slow cook on LOW for 6-8 hours. Note: Brisket is a tough cut of meat so for best results, cook it on LOW setting for longer period of time. Larger brisket may need 10 hours of cook time in a slow cooker.