Many, many moons ago, I bought a set of written off computer equipment from the US embassy here in PY. One was a server that had 7 (SCSI) CD players in it. Stripped out the motherboard and drives out of it, my interest was the case. Mounted a much more modern motherboard in it and put in 5 HDDs, one to boot from, which is in the only HDD slot, the rest of the drives went into the section where all the CD drives used to be.
But those are 5.25" devices and HDDs are 3,5". The CD drives had no use for me, so I dismantled all of them completely. The external housing was then cut up to make the 3,5" drives fit, but not so much that it would not fit the 5,25" bays anymore. The server is 10+ years in operation.
If you have an old CD/DVD player that you aren't using anymore, you can strip all the hardware out of it and mount both 2,5" drives sideways in it, much farther away from each other, with no need to actively cooling the drives. Still, in case you consider active cooling, you could cut and bend parts of the metal, so that you can screw a case fan (upright) onto it. And then mount the contraption inside the case through holes in the bottom (or top) of this case.
If there are holes in the bottom of the case, those could be there for air flow into the case. If you think that is the purpose of these holes, don't block these.
Quite a "hobby" project, but as long as it works (and it is out of sight), who really cares?