New hobby, new problems - eviltoast

Ok, if this is a dumb question, please let me know.

VERY new to homelab, career is changing so I’ve been meaning to get into it. Have been using my gaming PC as a plex server and have been interested in building a separate system for a while.

Purchased a Dell Optiplex 5060 MT and realized I only have space for one 3.5" HDD and one 2.5" HDD. I’m currenlty waiting on that as well as two 18TB 3.5" hard drives, (one for data, one parity) and waiting to purchase more once I start to close in on 18TB.

Is there a simple way of just STORING these hard drives outside of the case while connected to Sata? Does it have to be a DAS? Does it have to be $120 and also plugged in via USB 3? I’ve looked at 5.25" bay converters and not many people(at least not well documented) have modded it to allow more than 2 total, and I still have an SSD(Half a terabyte) that I have to fit for my cache folder.

Any suggestions on making this work? Or maybe other posts where they had this issue? I had trouble searching as well but I’m afraid fitting stuff in the optiplex wasn’t a common as an issue as I thought.

Thanks!