A few years ago I cut much of my stash up into pre-cut sizes, so I have a bunch of squares and strips all ready to go. Maybe you have some too, or some left overs from collections to use.
Using a serger makes this extra fast, especially the ties! I don't use the serger on the side seams, as I want them to be extra strong. But if your serger will do extra-strong seams, you could serge the side seams too.
If you don't have a serger, you could stitch the mask top and bottom edges 1/4 inch under; and for the ties, you could fold the strips in thirds and zig-zag them.
One-quarter inch seam allowances are used. The casings for the ties are one-half inch, as you will see below. In the instructions, I say "sew" when the seam is done on the sewing machine and "serge" when it's done on the serger."
Choose a ten inch square and cut it in half.
Sew two of the short edges together, right sides together, being sure to back-tack at start and end of seam. Don't sew the other end,
Serge down each of the two long edges (single layer of fabric), shaving off just a whisker as you go.
Trim off the serger thread tails and then sew the other two short edges, right sides together, again being sure to back-tack. Turn the piece right side out and press.
Referring to the red line in this photograph, sew a box shape going around all four sides of the mask: use a 1/4 inch seam allowance at the top and bottom (long sides) BUT be sure to sew 1/2 inch away from the sides. This creates the casings, so be careful not to sew across the top and bottom of them. Strengthen the casing seam by back-tacking on both ends.
You could choose NOT to sew the top seam, but to leave it open in order to insert a filter, if you have some.
Choose one of your 2 1/2 inch strips and cut it in half lengthwise, so you have two 1/1/4 inch strips.
Iron them in half lengthwise, right side out. Serge the raw edges together, shaving off a whisker's width as you go. Trim off the thread tails. I usually pink the ends too.
Use that very high-tech sewing accessory, the safety pin, to insert one tie through each casing, knot the ends of the ties.
And done!
I am not going to post a picture of myself in one of these masks because I have not had a haircut in about 10 weeks!