From: https://m.youtube.com/watch?v=vKwg1E1c6_Q

I’m too cheap to buy either of the Sophie patterns, but I can see myself using this i-cord selvedge on other projects. Knowing my memory to be sieve-like, I’m hoping that the act of swatching and creating a project page might help me to remember it.

E-loop cast-on to start and to increase.
What I did:
Cast on 6.
K3, slip 3 with yarn in front.
Repeat that row a bunch of times.
K3, inc, sl3 wyif.
Turn, and repeat.
K5, sl3 wyif.
Repeat that row a bunch of times.
K3, inc, k2, inc, sl3 wyif.
K7, sl3 wyif.
Repeat that row a bunch of times.

Intended uses:
neckline of sideways knit shawls and scarves, such as:
https://www.ravelry.com/patterns/library/zag-edged-scarf
https://www.ravelry.com/patterns/library/pimpelliese
https://www.ravelry.com/projects/JessicaJean/as-you-like-...
https://www.ravelry.com/patterns/library/spring-cleaning-2

One side selvedge on: https://www.ravelry.com/projects/JessicaJean/golfbabas-st...

Both selvedges on straight items:
https://www.ravelry.com/projects/JessicaJean/peach-laprobe

or just continue on 6 stitches to make a thick/ flatish cord. Could be used as a hairband or belt.