Do not turn the work whilst making the i-cord cast-on. When you do the kfb, keep the yarn quite taut as this is where the i-cord closes in on itself.
Cast on 3 stitches then *kfb, k2. Slip 3 sts back onto LH needle and repeat from * until you have two stitches less than the required number of stitches on the RH needle, and 3 stitches still on the LH needle.
Place the last two remaining stitches on a stitch holder, or tie them up with scrap yarn. When it is time to finish the garment, use the tail of the cast-on to sew in these two stitches to the beginning of the i-cord cast-on. This will help make it look like the i-cord is continuous all around at the cast-on edge.
On the next round, if you find the stitches created are a little large, work into the back of each stitch to twist and tighten it.
Cast on 3 stitches then [k2, k2togtbl, sl3 back to left needle], repeat as required.