It might be worth it to look into 3.5" drive enclosures. I've got an aluminium one which is a little oversized for a 3.5" drive and which has just the right size for a NUC board and some 2.5" drives (30mm height in total).[![Picture of mine.][1]][1]
 It even has a status LED (that's the cable you see) and a kind of sled onto which I can mount stuff.

  [1]: https://i.sstatic.net/daMUK.jpg