1) Cut two of each of the mask and liner patterns in material; stitch the lead edges of each together, be sure to lock your stitch ends.
2) Iron both un-stitched edges of just the liner material into a double hem.
3) Stitch both double hems, be sure to lock your stitch ends.
4) Face both exteriors to each other, pin and stitch them. Be careful at the nose and chin to make sure you don’t stitch the front down.
5) Fold inside out, and add 3” piece of wire, twist tie or pipe cleaner to inside top edge.
6) Stitch top and bottom edges making sure to get wire inside top edge stitching.
7) Double hem both sides of outside material, it should come right up to the inside material pocket hem, then stitch as close to the inside as possible.
8) Fish a 10” piece of thin elastic through the front material outside hems.
9) Tie elastics, and then put a slight bend in the nose wire.
Blue shop towel filter
Below is an article about double thickness blue shop towels as an N93 equivalent filter.
Each roll is 58 sheets. Split in thirds, folded in half, and stitched is about an N93 filter. (So each filter is a little more then a cent each).