I think they're assuming you already know how to make an i-cord. They're not giving instructions for how to make one, just telling you to do it. I would do a regular i-cord. If you knit it flat, you'll end up with a flat strap.
Mommy to two wonderful girls
"I don't have to conform to the vagaries of time and space, I'm a loony!" -Campbell Bain (David Tennant) 'Takin' Over the Asylum'
OTN: Cabled Sweater
, arm warmers, kids' clothes