I remember learning to do this stitch with some kind of homemade spindle in Camp Fire Girls probably about 4th grade. Here's the step by step in video.
I usually use one strand of yarn for each color that is in the handbag to make a pretty sturdy i-cord. I-cords are like a braided rope when completed. If you plan to felt the i-cord make it 1/3 longer than the finished length you plan. if it needs to be 24" long add 8" before felting, it shrinks that much ... then stretch, stretch, stretch it so that it is back to 24" this makes the item very sturdy. ENJOY.