Alright, don't mind "the frizzies" here. Just look at the basic idea, not the presentation. :)
You can do this in so many different ways. I did two inside out french braid cornrows on the side, then joined them with an elastic at the top. (If you don't know how to do an inside out french braid, look under my "quick search labels" for "videos." You'll find an instructional video there!)Tie the ribbon onto the elastic and pull it underneath to hide the knot.Start sewing down the first braid diagonally. (With a needle.) When you get to the end, turn right around and come back up the braid, sewing diagonally in the opposite direction to form the X's. Do the same thing with the other braid, then tie off the ribbon back onto the elastic when you're done.Add a bow, and that's it!