Well, that is about to change.
This DIY Mask Dispenser video byDrink and Sew Thingshas changed my mask organization for good.
Step Two
Install your sewing machines zipper foot on the right side.

Be sure its on the right side to start so you might sew more on the left.
There is a hack in the video to easily sew the end of the zipper on.
Step Three
Align and pin your fleece to the zipper.

Drink and Sew Things via YouTube video.
Step Four
Sew the first side of the zipper on the fabric.
Repeat step three and pin the opposite side, then sew.

Step Five
Unzip your zipper, and flip the fabric inside out.
Pin the fabric together to sew the rest of the bag.