What is the best way to store stencils?

I got foam board at the Dollar Store and started grouping them by subject matter and using the boards to keep them flat. I cut them to size and used spring clips to hold them together.

Because there were so many of them, I actually hung them from the ceiling in my basement.

I hang mine on a peg board. That works well for me. You can also store them flat.

Roll them and put in Tubes

I store mine in a photo album. They come in various sizes, my largest will hold a 10.5 X 12 inch stencil.

I store flat between a couple foam core poster boards. Mine are underneath my bed.

I don't know how big they are but I use as zip lock bag and lay flat.

https://www.youtube.com/watch?v=uGHWwooM-Ko

I use an accordion folder with about 20 pockets. 😇

Depending upon their size, sorting them in folders and placing them in a filing cabinet works well. If you don't have a filing cabinet, they're pretty easy to fine in resale stores. You can file all kinds of keepsakes, large photos, product warranties, even recipes, all with the vital statistics and documents you would normally file in a cabinet. I love my filing cabinets. Knowing that everything that needs to be stored flat is in one place I always know where to start looking.