Rinse your brisket and pat dry. Place in slow-cooker, add seasoning packet, and cover with water. Cook on low setting for at least 8 hours.
Just before you're ready to eat, heat broiler to high heat. Trim off any fat on the exterior of brisket (it should fall off pretty easily after cooking for 8 hours). Remove brisket from crockpot, placing in a baking dish.
Mix together honey and mustard and pour directly over the top of brisket, coating evenly. Broil for 5-7 minutes or until the glaze begins to brown and caramelize.
Slice and serve.