I'm not making a sweater, mind you. So, I summoned the powers of Google, and brought up a description in words and a video of how to do it.
First, I checked to see if I wanted P1, K1, ribbing, or K1, P1 ribbing. It was K1, P1, thankfully.
Pattern said you were to do a slip knot on the needle. Easy enough. Then knit in the stitch, leaving the old stitch on the needle. Simplicity. Pop the new stitch on the old needle. Dirt simple.
Then - things got - funky. You're supposed to be knitting between the loops of your cast on, or purling between the loops. You bring the yarn forward or back to knit or purl as usual.
Other than the fact that I look like I'm doing a ton of work for very little effect, the cast on doesn't look that bad. Time will tell if it actually works.
The first few cast on loops though - they felt like mental moebius strips.