Actually I made it around 10pm the night before her fourth birthday party. I was in a hurry so I used fabric-tac glue instead of sewing it.
Last year it was blazing hot, so we celebrating inside.
All I did was cut a length of twine to the length I needed and then cut triangles out of my stash fabric. I used pinking shears too keep the fraying of the fabric to a minimum. This year they were hanging outside for a couple of days through wind and rain so the edges have been softened.
I also trimmed the top corners off a bit so they wouldn't overlap and show from the front. Then I glued them around the twine.