Cut 2 rectangles of fabric:
Main: 7.5” x 11.5" (child size; 6.5" x 10")
Lining: 7.5” x 10" (child size; 6.5" x 8.5")
Optional: 7.5” x 10” interfacing (child size; 6.5" x 8.5")
Center lining over the main fabric with right sides facing.
Flip both pieces over and fold excess from main fabric back over itself. Press folds.
Mark 2” in on each corner (1.75" for child size).
Cut corner triangles off.
Unfold excess sides of main fabric and snip the little triangles off.
After cutting out fabric...
With right sides together, using a 3/8” seam allowance (1/4" for child size), stitch corner, top, corner and corner, bottom, corner; leaving sides open.
Turn right sides out through one of the sides and press. I let the casing fabric form angled edges.
Note: if you would like to add a nose wire, now is the time to do it. Simply mark where the nose wire will be placed, sew 2 sides of a 3 sided channel. Keeping needle down in the fabric, lift the presser foot up and, through the side of the mask closest to you, insert the nose wire in the channel. Lower presser foot and complete 3rd side of the nose wire channel. (I'm hoping to add pictures of this step soon!)
Evenly fold top and bottom to the center. It should be 3” tall (2.5" tall for child size).
Measure 7” in the center and mark for sewing (6.5" for child size). Then, sew the flaps in place by sewing a rectangle (3”x 7”) in the middle of the mask (2.5" x 6.5" for child size). The rectangle secures the flaps in place while also top stitching the main part of the mask.
Fold edge over tie.
Fold over again to create casing and pin in place.
Stitch casing closed, catching the tie in the seam.
Using a tapestry needle, thread ties through casing. If you don't have a tapestry needle, you can use a safety pin.
Tie a knot in the end of each tie.
Iron the flaps down on the mask.
You can fold it like this and pop it in your back pocket: