Begin by making a crochet chain that has a few more chains than the number of stitches you need to cast on. FYI, this is some leftover handspun from my Zora cardigan. Not sure why I'm wasting it on this, but it was sitting in my leftover basket so here it is.
When you have enough chains, cut the waste yarn, end the chain off, and tie a knot in the cut end, like this.
This isn't strictly necessary, but it helps to identify the end of the chain where you will begin the unravelling process later on when it's time to work in the opposite direction.
Now, have a look at your chain. On the front side, you have something that resembles a braid (see above), but on the back side notice what looks like a series of purl bumps.
After a while, this is what will emerge. See how the braided front side of the chain runs along the bottom of your stitches? Keep in mind that these stitches count as your cast-on, not as the first row of knitting.