[Build Help] Need help with HDD setup. Can I stick it to the side of my case like I did with my SSD?

Here is my setup. I want to get a small HDD in there because my SSD's are running out of room, and I wanted them to only have games. One Crucial 128 GB drive is a boot drive only with windows update data and the other is for Steam games (which is pretty much at 70% capacity)

Can I mount a small HDD like I did with the SSD in the picture shown? Or can I simply lay it down at the bottom of my case.

I know it's not aesthetically pleasing, but I don't think it'll affect airflow or anything.

Edit Please excuse my horrendous cable management...I have a Lian li A05FNA, which looks sleek and minimalist on the outside..but cable management is non-existent/impossible with it.