Found other designs but the base size were smaller. So I made my own design. I'm not sure if this is because the iMac was the 27inch and might have a larger base. I know this fits on the 27inch iMac and iMac pro. If any one knows about base size on the 23inch please leave in comments. The design can be scaled taller for people who are taller. Just remember to scale the drawer the same percentage as the base. Currently its about 2 inches tall.
I will be making a future design with a hole in the back in case people want to use the drawer for a back up hard drive. As well as a taller version that may have two drawers.
The models imported into thingiverse standing up but I would print them right side up like how it would be used. Support only needed on the hole in the drawer. Unless your printer does well with short bridging. Infill can be less but by default i always print around 20%.