TL/DR:
* 27cm x 19cm fabric
* on the 19cm sides, fold 1cm and stitch
* on the 27cm sides, fold 4cm and stitch a wide tunnel
* 2 @ 60cm laces; each through a tunnel and tied to self in a loop to fit over ear
* Adjust each loop for custom fitment

https://jezra.net/post/2020-03-17_sewing-a-face-mask.html