Remove corned beef from package and locate the seasoning packet. Set the included seasoning packet aside. Rinse the corned beef.
Pour the Guinness into a slow cooker. Add the seasoning packet, bay leaves, brown sugar, beef bouillon, coriander, cloves, mustard powder, allspice and Worcestershire sauce. Stir to combine.
Add the corned beef with the fatty side up. Cook on low for eight to 10 hours until the corned beef is fork tender. To serve, slice against the grain or shred with two forks.
For a festive St. Patrick's Day celebration, try this slow cooker Guinness corned beef. This crowd-pleasing, easy recipe will make entertaining a breeze.