Cut two rectangles of fabric from the bags. These should be about 5 1/2 inches by 7 inches. The size will depend on the size of the person but I would start large and cut down to fit if needed.
Add ribbon to both sides. This can be two ribbons or one long one looped at the top as shown. Then glue down both sides of the fabric and allow to dry. If you are adding a filter, glue along the bottom as well but leave holes for your ribbon. Leave the top open to insert the filter and change it.
To put on, put top loop on the top of your head then pull the mask over your mouth. Pull the bottom strings around your neck and tie. You can adjust to fit if needed here. Trim smaller if needed or add pleats with glue to the sides.