Here is a demonstration of how to sandwich cord between two layers of rice paper.
First of all tape white plastic trash bags with no print to your art table. Place a sheet of rice paper on top of the plastic. Then place strips of cotton cording vertically and then horizontally on the sheet of rice paper.
Or you could lay your string on the paper in any design you like.
Then place another sheet of rice paper on top of the string.
Now spritz with water till it is nice and damp but not drenched.
Now pour some matte medium on top of that. When it dries, it will have somewhat of a milky look to it. If you would prefer more of a transparent look, use gel medium. I would suggest trying it both ways to see which look you like best. I'll be doing the gel next time myself.
Very gently spread it around with a damp paint brush to cover the entire surface. If you get a little tear in the rice paper, not to worry; it will just give it an interesting look.
Let it dry completely before removing it from the plastic. When it is dry, just peel it off. You could then use it the way it is in whatever project you need it for, or you could paint it.
I left one unpainted and I painted the other with several different colors so that I would be able to just use bits and pieces for collages and have a variety of colors available to choose from.