The only space I have is in a cupboard stored vertically, but they’re clumsily leaned against one another other.
UPDATE: Thank you for the suggestions everybody! I ended up finding a metal thing, almost like a file organizer, from value village for $2 that worked perfectly.
I have some Command strips jewelry knobs that I have attached to the top of my cabinet so when I slide my tall sheets in they catch on the knobs and stand up. The shorter sheets kind of rest on the tall ones.