No, it isn't FSL. It looks like it is an in the hoop project. It should stitch out fine on one layer of good quality felt and using 2 layers of Solvy or wss Vilene.It only has 6,800 stitches.
This is her link
I don't know how to find that without a link to the page. Do you have a link?
I think I would use organza, but I am still a beginner. I am sure someone else is going to answer pretty soon.