I-cord is traditionally knit with knitting needles. It is possible to make an i-cord of many different gauges and densities depending on the yarn weight and needle size, which makes this method of i-cord making the most versatile. I started with cotton worsted weight yarn and one size 8 circular needle (two double pointed needles work as well).

There is a little gap that happens at the back of the knitting where the yarn is brought back to the front, but this disappears when the cord is stretched and worked and the loops settle in. Somehow, near the end of the cord I added a stitch to have five instead of four. Hm.

In 30 minutes I made 18” of cord, which has a little more body than the crocheted and dolly knit versions. It has 25% stretch (18” stretched to 22.5”).
I think I will experiment with yarn weight to needle size variations of i-cord. I actually prefer my cordage to not have much stretch. Experiments will continue.