I just cut fresh cabbage, mostly green or all green with a knife.
Grate carrots, red onion, and whatever nobody hates like turnips, radishes, broccoli stems, and bell peppers. Just make sure it's mostly green cabbage.
For dressing I mix Trader Joes fat free cole slaw dressing with ranch dressing from a package mixed made with buttermilk and sprinkle with celery seed.
Easy and we like it much better than the store bought kind.