Foo Fighers are one of my fave rock bands. I like them so much, when I hear them in public I embarrass myself trying to sing like Dave and do very weak air guitar poses with my Mr Burns like wrists hehe : )
In a regular braid there are 3 strands. For this look, all you do is braid one of those strands beforehand and loosen it up with your fingers, then braid as usual. This creates extra texture + breaks up the mundane pattern of a regular braid.