Open up the package and place the contents in a large bowl.
Now in a separate bowl combine the Miracle Whip, sour cream, celery salt, mustard flour, vinegar, black pepper and sugar and whisk it until it becomes nice and creamy.
Add the Miracle Whip mixture to the shredded cabbage and carrots and then mix until the slaw is coated. Then cover the bowl and refrigerate for a few hours so that the flavors all get happy. Enjoy!