Finish the seams

Turn the mask upside, check that the seams hold correctly.

Sew a seam all along at 1cm / 0.4in from the edge in order to keep the fabric layers together during washes. Start this seam on the top edge at 2cm / 0.8in from the right or left edge. Follow the border around and finish on the other side at 2cm / 0.8in from the edge.

This way we keep a large opening to slide in our filter, which will be well maintained.