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.
You could maybe utilize a heavy bookend?
Desktop file organiser or dish drying rack.
File orfanizer turned on the side for vertical storage
Our cupboard has little grooves top and bottom, and we have little wooden dividers that go into the grooves, so we can make as many sections as we want. It was a custom build, but I don’t see why it would be hard to add something like that after the fact by taking down some slats with the grooves cut into them.
I see there’s also a lot of products like this one.
There are racks you can buy in the kitchen section of many stores designed for this very task. Have you tried any kitchen stores? Bed Bath & Beyond was the obvious choice here in the USA, but they went bust this summer.
You can also 3dprint this if you or someone you know has a printer. There are a few designs on thingverse, or you could design your own with some CAD software for specific dimensions of your baking sheets. I printed one a few months ago for my cutting boards.
Some people use spring-loaded curtain rods installed vertically in the cabinet. This creates divided space that the sheets and boards can lean against.
Ikea has the RINNIG or OSTIG plate dish racks They also have the VARIERA pot lid organiser and the UPPDATERA customisable kitchen organiser.
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.
Vertical mesh filing holders work great if they aren’t big. Cost like a couple of bucks at local office supplies.
I installed a wooden strip down the middle for that exact purpose
