Pattern available here:
 https://www.askcosplaysenpai.com/products/diy-medical-mask-pattern
There is an optional $3 donation, but if you need a pattern and can’t afford it, it is also available for free.

This is a quick step-by-step guide to the pattern on my website.  Mask making is a great stash buster, and reversible ones give you even more style options.