I built a mini homelab using 6X5 gridfinity unit blocks.  It's stackable, modular, and doesn't require any hardware.  I've been running this for months with no cooling issues because the back side is compelteley open.  The gridfinity comes out just shy of the standard 10 inch server rack hardware standard, so storebought 10 inch rack items don't quite fit.  The only part I bought was a 10 inch patch panel from amazon.  I just removed the front plate and made this new housing.  You can print and glue on the ID tags as well.  I included a blank.  Just add text in the slicer.  The print quality in my model was pretty janky because I did most of this on my old ender 3 before I really new what I was doing.  I'll probably reprint eventually but wanted to share this as a proof of concept for anyone interested.