Raw Material Storage Ideas

I’m a newer user and am looking for a way to organize all the 12"x18" pieces of material we have acquired for our future projects. Right now I have them standing on end in a milk crate (since we are a milk processing plant, that’s what we have lots of). It actually fits pretty well since they are 12" wide on the inside. So, I flip through the stack from the top kind of like looking through a filing cabinet. However, it gets a bit unstable when the most of the stack goes to one side and 3 crates takes up more floor space than I would like.

I think I would rather they be standing on edge in tall narrow compartments like the picture below. Does anyone have a shelf or rack system or other method that is working well for them? Thanks!