When I first put in an above-ground pool, I didn't have anywhere to store the supplies, so I built a small parts caddy. It was cool - served the purpose. Then I built a small deck and ladder to get into the pool. Again - cool; served the purpose. I knew I wanted to tweak both, so recently I mostly dismantled both and combined them. Both pieces were made out of all upcycled products - the vast majority being pallets with small decorative bits being some leftover fencing we took down. Both original items are also uploaded to 1001pallets if you're curious.
I enclosed the raised deck/ladder structure and added a door for accessibility and more protected storage, and also removed the deck boards and turned them into a lid. I added a set of shelves to hold crates for the pool chemicals so they'd be easily accessible, and then finally added some hooks to hold the poles, brushes, and the like. The enclosed area also hides a convenient trash can for when those chemical containers are empty - so the dogs don't get into them! :-D I then painted it all with some exterior clearance satin. It's a very expensive name brand that would usually run over 120.00 for a five gal bucket, but I guess the color was icky to the original customer, so I got the five gals. for 9 DOLLARS! The bits of hardware are all reclaimed from various things - so this whole thing didn't cost more than maybe about 2 dollars?
There was no plan, blueprints, etc... I don't build that way. I'm just a backyard tinkerer - a nurse by profession, and make due with a few essential tools - a cheap table saw, a hand saw, an impact driver & drill, and an ancient router with an embarrassingly scanty assortment of blades. But, with all that, this is a sturdy, functional unit that has already been tested out. :D