I wondered what to do with all the older 3.5" HDDs in my office. I tried some other solutions to stack them but it was not that simple way I needed it to be. Now I am able to stack them with a minimal need of material.

Just print it 4 times for one HDD and mount them over another.

I am using USB 3 to SATA connectors which I bought from amazon and now I have more space and all the HDDs have a meaning. Win win :)

By the way - theres enough room between the HDDs so they are not heating up that much.