If you were making this design for other people. you would want to form the mask on a mannequin, instead of using your face! (edited)
Pretty neat design, very minimalist, could be easier to put together, for instance, we could have two mating parts that have a locking mechanism which can punch through this thickness of cloth so the two pieces could just be snapped together. The flatness is also an issue but I feel that it can be compensated for by going with a larger fit.
Nice work! (edited)
After adding each rubber band, press the mask against your face tightly again and then fasten the next anchor. Then, trim the excess cloth, punch holes with a miniature screw driver and tie on some ribbon for tying the mask.
Hold both printed pieces tightly together (only the top piece shown here) and form it against your face, forcing the cloth to conform to the shape of your face. When you take it away from your face hold both plastic pieces together tightly with the cloth sandwiched between and add a rubber band to one of the anchors. (edited)
One on top and one on the bottom of a blue shop towel, folded as shown. Face them with the smooth bed side of the printed part toward the cloth so there aren't sharp edges on your face.
Two printed pieces, one shop towel, four rubber bands and four pieces of ribbon. (edited)
I printed this. I have 40 or so pictures (but I'll keep it pithy with 4 or 5) how I made a not so good version and then secondly, a better version with blue shop towels, rubber bands and ribbon. Instead of using one piece, I printed two pieces and then sandwiched the towel between the two pieces and used the anchor points for rubber bands. Then punched holes through and attached ribbon.
The most important step is after you've sandwiched the filter between the two pieces you need to press your face into the mask so that enough cloth is squeezed through to contain your face. Then rubber band one anchor, push your face into it again, hold it and add the next rubber band, etc.
I'm a 5'10 male. I printed the medium size but it felt small, I'd go for the large if you're printing this for the first time.
This design respects speed and filament. It's not as easy as sewing a mask (if you know how to sew (and have a sewing machine)) but I think it is a pretty decent way to make a mask quickly if you have a 3d printer. (edited)