Wow, paper with grass in it, who would have thought? Very cool!
I have a little Porter Cable furniture staple gun. Shoots 1/2" wide staples with whatever length legs (3/16 – 1/2 I believe) You could glue and staple them across the back, works good for this sort of thing since you don’t see the back. (Food for thought)
Figuring out how to do something you have never done is what makes a good challenge.