Wrap the sash around the front of the chair's backrest around to the back. Cross the ends of the sash so the right end faces to the left side of the chair and the left end faces to the right side of the chair. Cross them so the left end of the sash sits over the right end.
Tuck the end of the left sash under the cross between the two sides of the sash. Pull both ends of the sash to tighten it around the chair and create a knot.
Make a loop with the right side of the sash as you would when you tie your shoelaces. Wrap the left side of the fabric around the base of the loop just above your hands that hold the loop in place.
Reach around the back of the loop and under the part of the sash that is wrapped around the loop. Reach through the loop and grab the left piece of sash. Pull the center of the left sash piece back through the loop until it creates a loop as big as the first.
Pull on both loops to tighten the knot between them. Pull them one at a time to even out their size if one loop is larger than the other loop. To make the loops smaller, tug on the hanging ends of the sash.