The CPU and FAN mounting holes are not square. You can not install it in any orientation. You must install it in the orientation where the CPU FAN’s cable is pointing out the top. Installing it 90 degrees in either direction, will cause only some heatsink posts to mate with the CPU fan, but not the other two. Installing it 180 degrees from the only correct orientation will mean that the CPU FAN cable will not be able to reach the CPU FAN header on the motherboard. Effectively, there is only one orientation that the CPU FAN can be installed – With the CPU FAN cable jutting out from the top.
I actually just tired to post this on the frame.work build guide but the UI froze up and I’m pretty sure that it didn’t complete the HTTP post. So I’ll put the text here instead.