Printer power unit slotted wall mount.

Recommended only if you trust the power supply not to heat up and melt the mount, and if the surface being mounted to can really hold screws. most critics would deem this an unsafe accessory, so refer to the comments for feedback and advice.
Screw the mount to surface, and insert the 4m screws on the PSU which hold it on the mount by sliding into the slots. Make sure the fan is blowing out away from your surface so that air access is unblocked.
Intentionally, this was for small spaces behind the enclosure of my printer, and I've been using this for one year, as it allows for the simplest way to dismount the unit. But as they say, "simplest is not always the best or safest choice." So far I'm not regretting it.