Start with your cut pieces. You should have two larger pieces that are the outside and two smaller pieces that are the liner.
First, put the right sides together of both pieces and sew along the curve. You can sew along the marked line or use a 1/4 inch seam allowance.
Clip all along the curve on both pieces with a pair of scissors but be sure NOT to cut into the stitches.
Iron down the sides on both the front and the liner. For the liner, turn over 1/4 inch and iron.
For the outer piece, turn over 1/4 inch and iron.
Then turn over 1/2 an inch and iron. This will make your casing later for the ties or elastic.
Then sew the liner as close to the edge as possible. Sew the outer piece as far from the edge as possible along that 1/2 inch fold. This makes the casing as large as possible.
Then press the seam down the middle to one side on both pieces. Top stitch this on that side as close to the seam in the middle as possible.
If you want to add a cute face or mouth to your face mask, cut the design from iron-on then weed away all of the excess.
Because the face mask is curved, I did one side at a time. So iron the first side to your mask.
Once it has adhered, peel back the liner and cut it off with scissors.
Then position the opposite side and iron.
Remove the liner once it has adhered.
Then turn over to the back and iron once more paying attention to the middle seam especially.
Then your iron-on should be on your mask and you can continue with the sewing tutorial.
Put the liner on the outer piece with the right sides together.
Align the seams and pin them into place.
Then sew along the top edge and bottom edge at a 1/4 inch seam allowance. DO NOT go over the casing on both sides.
Turn right side out through one of the sides (both of these should be open). Then press the seams.
Top stitch along the top and the bottom as close to the edge as you can. Once again you DO NOT want to sew closed your casings on the side.
Then add a safety pin to one side of your elastic. You can substitute ribbon, string, t-shirt strips, ribbon, shoestrings, and more here
Use the safety pin to feed the elastic through both casings. Then you can use a zig-zag stitch to secure the pieces together to complete your mask. If using an alternate, cut it longer and leave the ends handing to tie it around your neck.