There is an explicit description of fuse direction on the Antipodes forum, here:
Fuse direction in K50, as follows (this discussion also applies to the fuse holder of CX/EX):
“Hold the red connector the way you would in order to insert it into the receptacle.
On the right side the direction is from the back to the front. On the left side the direction is from the front to the back. This is true whether 115v or 230v.”
Before replacing these fuses it is also relevant to check the value of the fuses that were in the CX and EX: In the original CX as well as the original EX both fuses are 1A, slow blow.
As far as I am aware, with the hardware upgrade in both CX and EX, which changed their power supplies, both fuses were changed to 2.5A, slow blow.