This is a 3 layer mask with filter pocket. The large size completely covers an n95 mask.

Supplies

100% cotton fabric, thread, needles, sewing machine, 4 inches of 20 or 22 gauge wire
FU mask pattern:
https://freesewing.org/blog/facemask-frenzy/

Step 1: Cut Pattern X 3

Fold your fabric in half, best to use 3 different fabrics to keep track. Cut 4 ties at about 18 inches long.
*Pro tip, if you're using twill tape, knot the end of the ties to prevent fraying.

Step 2: Sew Body Pieces at Center.

Starting at the top of the curve, sew along the curve of each layer. My seam allowance is the width of my presser foot. It's about 3/8 in, and I find it reduces bulk.

Step 3: Make the Filter Pocket

This fabric will be next to the face. I've chosen a solid. With the seam showing, fold one edge over twice, about one finger width each time. Sew the seam.

Step 4: Place Filter Pocket

Place the filter pocket inside of the inner layer. The RIGHT SIDE of the inner layer should be touching the WRONG side of the pocket layer. When you look at it, you should see the pattern of the liner and the finished edge of the filter pocket.

Step 5: Place the Outer Layer

Place the outer layer in the center RIGHT side in. You will now have a 3 layer sandwich.

Step 6: Sew Layers Together.

Starting at the end of the top, stitch your layers together. I find it helpful to sew to the peak, sink the needle, then turn for the down curve.

Step 7: Sew the Bottom Edge.

Sew along the bottom edge, again at the width of your presser foot.

Step 8: Turn the Project Right Side Out

If the raw seam is showing, it's okay. Just turn it again. Treat the filter pocket as one side, and repeat. Your final project will show only finished seams on the inside and outside.

Step 9: Top Stitch the Bottom Edge

Run a narrow topstitch along the bottom edge

Step 10: Prepare Your Wire

Cut a 4 inch piece of wire, and curl the ends. (this keeps the wire from destroying the fabric after it's placed. This is important!)
Mark the ends of your wire channel on the mask, use pins, pencil, marker - whatever.

Step 11: Make the Wire Channel.

I set the needle at the bottom edge of the channel and backstitch to the top, then stitch down to the bottom of the channel and turn. Stitch to the end of the channel, but DO NOT TURN. clip and remove from the machine.

Step 12: Place the Wire, Seal It In.

Slide the wire into the channel from the unfinished side. When the wire is set, sink your needle at the base of the channel, backstitch, then forward stitch until you have completed the channel.
*Optional - topstitch the upper edge.

Step 13: Add Ties

Use your fingers to fold in the raw edges on the short side of the mask. Place ties in the seam allowance. One at the top, one at the bottom. Make sure you backstitch over the ties. Repeat for the other unfinished edge.