I am using a 7" zipper. I separated it and use both sides or even three pieces for a bigger one. I am just using what I have I am sure a longer zipper would work better. I can wait until tomorrow I have some new zippers I got from a garage sale that are cotton with the cute metal zipper teeth. The soft cotton will bend much better than this stiff polyester.
Any way I should push on...
I begin by rolling a tight center two or three times. And tack it with needle and thread.
As you go you will want some nonuniformity (is that a word?) so I fold the zipper backwards and start going the other way.
To give it more body I did some gathering stitches along the bottom as I wound the zipper around. This makes it pull in nice to the center but still lets the top zipper part flutter out like a petal. Does that make sense?
Here we are all wound up
Three together, I glued them to a piece of felt. I will trim the felt and use on a headband or barrette.