Another mask tutorial that is. Here are the parts I do remember about it.
It was a pleated mask using 3 pieces of fabric, the front piece and 2 lining pieces. The 2 lining pieces were put right sides together and stitched approximately 1 1/2 inches from each side. This leaves an opening in the center of the two pieces.
The the 2 lining pieces were folded so that they right sides out. One piece of lining becomes the top and one piece of lining becomes the bottom piece. The linings are cut two different sizes. Both pieces seamed together now equal the size of the front piece for the mask.
You can easily top stitch along the 2 lining pieces as they lay flat on the machine bed. You don't have to top stitch through a tube type opening.
Here is one tutorial that shows the top-stitching method I am trying to avoid. Yes, I could do it this way.
https://www.youtube.com/watch?v=zz0YpY6VqVU
Do you remember it? I've exhausted my searches so far.