Extend your right arm all the way out while holding the end of your obi in your right hand. With your left hand, stretch the sash from your right hand to the middle of your chest.
Fold the stretched section in half. Put the folded end of the obi over your right shoulder and make sure the open end of the folded section hits at your waist.
Wrap the rest of the sash around your waist two times. You may want to hold onto the folded section so it doesn't slip down and open while you're wrapping the other end of the sash.
Fold the open end of the sash upward so the fold is pointed toward the floor. It should make a triangle shape.
Tie the two ends of the sash together so that the end you folded in half in Step 1 comes out on top.
Unfold the bottom end of the sash and pinch it in the center with your fingers to make a cute bow shape.
Take the end of the obi you folded in Step 1 and pull it down over the center of your bow and up and around the back of the bow.
Roll up the extra length of sash toward yourself and tuck it inside the obi so it isn't visible.
Suck in your tummy as if you're wearing your skinniest jeans and carefully slide the obi around you so the bow is in the back. Voila!