Once the four sides are sewn together, you can turn the mask inside out, and it will be complete. She suggests trimming the corners off (obviously without touching the seam itself) so it will be easier to turn it inside out. 

To make the mask pleats, Erica folds down the mask into three, three inch sections. She uses the clips to keep the pleats in place, and she then sews the edges of the mask to secure the pleats. 

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