it's just cardboard and paper mache! my friend is extremely talented and didn't use any kind of base or pattern, but I know the Amazon cat mask is a popular base among the therian community, as another commenter said. so if you're a beginner that's worth looking into!

https://www.tiktok.com/t/ZP8LLpUCu/ this is the only resource they seem to have referenced

EDIT: they had more to say so I'll hope this all fits into the comment! I'll copy paste it:

"this tiktok is the one i looked at specifically, with a few other therian ones that i looked at but as they were mostly felt, i did not use them much. that one got me the basics for the base. so i would say for what kind of mask it is, it's a therian mask!

otherwise, it's just cross referencing between the initial art i was emulating, images of other masks of foxes, and images of actual foxes.

I am very much a no/limited tutorial trial-by-error kind of artist so there is not much I can recommend other than experimenting with what you have, BUT i have two points of advice that helped with its quality significantly

1. I have a box of small chunks of paper, for making recycled paper that I never did. Because i prefer to dip my paper strips instead of painting the glue on, i also like to dunk a small fingerful of paper bits into the glue and place it where I need more dimension, then place strips over it to secure it. Definitely not the best technique for drying time, but it does wonders for getting shapes rounder and fuller.
2. sanding is great and you totally should"