My sister-in-law sent us two masks that she made back in March. We also had two cloth masks that my mom had made for us (with elastic around the ears), so when we needed more we had some experience with two different styles. My husband and I prefer the style with ties, so I knocked off the ones my SIL had made to make six more.
These masks are made of two layers of quilting cotton. I started with a double-layer rectangle, 6.75" wide and 6" tall finished at the top and bottom edge (raw edges on the sides are fine, since they'll be enclosed in the bias tape ties). I ironed in three evenly spaced pleats in the middle of the mask, so the finished pressed height is 4". Then for each mask I cut two one-yard lengths of 1/4" double-fold bias tape, folded the ends inside, and sewed along the open side of the bias tape, enclosing the side of the mask in the middle. By far the most time-consuming part of this was pressing the pleats in the mask.
I made this round of masks using all materials that I already had on hand. The limiting factor was the bias tape - I'm totally out now, and I couldn't find more online for a reasonable price/in reasonable quantities. We need some more masks - I'd like to have about 20 by the time I go back to work in mid-August so we won't be scrambling to get mask laundry done all the time - so I'm going to try making my own bias tape using this tutorial.
These masks have been working well for us. One of my husband's coworkers admired them enough to ask if I was selling them (I'm not, but I will make a few extra in the next batch so my husband can give one or two away at work)!