In a 6-qt. slow cooker, combine potatoes, carrots, celery and onion. Add corned beef. Place cloves, peppercorns and bay leaf on a double thickness of cheesecloth. Gather corners of cloth to enclose seasonings; tie securely with string. Place in slow cooker. Pour stout over top. Cook, covered, on low 8-10 hours or until meat and vegetables are tender, adding cabbage during the last hour of cooking. Cut beef diagonally across the grain into thin slices. Serve beef with vegetables and horseradish.