If you just use batteries and wireless, then that’s the end of the story.
But most of the time, this needs some cutouts. Let me describe how I created a custom version with a standard low-voltage power jack and an RJ-45 connector, using just these tools:
First step is to very carefully mark the position and saw some thin slots in this thing. ABS plastic is very soft and easy to cut with a little saw like the one above:
I tend to make the cutouts too narrow, because there is no way back!
To get a clean break, I use the knife to scratch along the line where the plastic needs to break, and then bend it (oops, you’ll also need some small pliers for that):
This coutout was in the top half, for the DC jack. After some trimming with the knife, the cutout looks pretty accurate. Next one was the RJ-45 connector:
Same idea: mark, saw, scratch, and break off:
Almost there. Still a bit too narrow, and not quite deep enough – some more trimming produced this:
Ah, that’s just about perfect (the left side could still be made a tad deeper):