This has been by far one of the most popular things that I've patterned. Print two copies, and sew them right sides together. Trim off the excess fabric and you can either put it on a beanie as a hat topper, or use it as a mask (halloween, cosplay, etc...)

I print this with 0% infill, 2 walls, and I make sure that ensuring vertical wall thickness is turned on. I print the first layer very slow, at 35mm/s. I pause at layer two, add fabric that is 12" x 12" held down by magnets, clips or tape, and resume the print. I use a 2 way stretch polymesh that allows for a comfortable stretch. The mesh grid allows great visibility when worn as a mask.

This is where I get my polymesh from.

https://www.joann.com/performance-nylon-spandex-power-mesh-fabric/16770323.html

This pattern uses the dragon scales originally modeled by Shoreydesigns.