1. Place first 2 ingredients, including soup mix seasoning packet, in a 6-qt. slow cooker. Trim fat from brisket to 1/4-inch thickness; make 1/4-inch-deep cuts, 1 inch apart, in fat. Sprinkle all sides of brisket with salt and pepper, and rub flour over brisket.
2. Cook brisket in hot oil in a large skillet over medium-high heat 10 minutes on each side or until golden brown. Transfer brisket from skillet to a plate.
3. Add chicken stock and 2 1/2 cups water to skillet. Bring to a boil, stirring to loosen browned bits from bottom of skillet; boil, stirring often, 1 to 2 minutes or until sauce is slightly thickened and smooth. Stir stock mixture into bean mixture in slow cooker. Place brisket, fat side up, on bean mixture. Cover and cook on LOW 7 to 8 hours or until brisket is fork-tender.
Note: We tested with Hurst's HamBeens Cajun 15-Bean Soup Mix and PictSweet Seasoning Blend frozen diced onion, peppers, and celery.