I've done one and used a shiny organzia. Turned out good & was really pretty. You can also use the fine tulle. Carefully trim after you are finished. I use a organzia that my little low watt sodder (however you spell it) tool will melt. But be careful or it'll also melt your thread! If you use a cotton or other natural thread, it won't melt. Hope this helps.
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Since they have a hanging loop you would think they are FSL but I guess you have to use organza or something similar for all those state ones and the wedding one too.
It was the loop that made me think they were FSL. I think I will embroider it on a strong stabilised fabric I have and cut it out without the loop. I wanted to make one for my grand-son....
I understand that they need a backing fabric. They are not FSL. You could use a leave in permanent stabilizer or felt.
I'm not sure if organza might work too.
I know she tried doing fsl originally but didn't quite get it right but people still wanted the designs so she kindly kept making them.