In a small bowl, combine garlic powder and pepper blend. Add seasoning packet included with brisket. (If no packet is included, use 1 tablespoon of seafood broil seasoning). Season both sides of the brisket with mixture. Place brisket on top of the potatoes, cutting to fit if necessary.
In a medium bowl, stir to gether Bass Ale, 1/4 cider vinegar, and mustard. Pour into slow cooker over brisket. Cover and cook on HIGH setting for 1 hour. Switch to LOW setting and cook for 4 hours.
In a medium bowl, toss cabbage with remaining cider vinegar and salt. Add cabbage mixture to the slow cooker, pushing down on top of the brisket. Cover and cook on LOW setting for an additional 3 to 4 hours.
Serving Ideas: Accompany with two or three small pots of different deli mustards. Makes a great sandwich the day after.