I couldn't figure it out either. I looked at their site at Secrets Of and didn't see details.

I've looked at these and thought the same as you! I think they must be stitched on WSS.

I do not remember what it is called, but there is a pencil shaped soldering/heating tool that can be used to solder around the edge of a
stitchout to smooth ragged edges. As I have never used one, just read
about it, it seems a possibility that was used in this case. A beautiful flower design!!
Hugs, Angel

I would think it's water soluble..that way some can be left in so you can shape that flowers. I'm not sure how you would shape them otherwise.

I would use WSS the thick one. Then just use a small paint brush with water on it to smooth out the edges . It should tear pretty clean anyway. Suzanne

I emailed the digitizer ,they used
Soft n Sheer Extra Fabri Solvy which is a Sulky product