This was originally designed for a Mean Well SE-600-24, but I've included the Fusion 360 (F3D) and STEP files if you'd like to modify them to fit your particular PSU. I used it to mount the PSU to 2 pieces of 2020 aluminum extrusion on the bottom of my printer.
There are 3 STL files: 1 for each of the mounts, and 1 plate that has both on it together. The reason for the 2 different mounts was originally I planned on having holes on the bottom to line up with the PSU's bottom screw holes, but they weren't needed, so I abandoned them.
The mounts in the images were printed in Hatchbox Blue PLA.
For assembly, you'll need (8) M3x6mm screws to attach the mounts to the PSU and (4) M5x8mm screws with (4) T-slot nuts to attach the mount to the extrusion.
Watch it print here: https://youtu.be/NyOsPuzZXZM
I printed this at 0.28mm to save time since this is a functional part that doesn't need to be pretty. The worse resolution you print it, the worse the holes will be, but if your printer is well-calibrated, there should be enough tolerance to get the proper screws through them even at 0.30mm. If not, you can always clean them out with a drill.
This was printed on a Eustathios Spider V2 designed by the talented +Eric Lien.