I'm making a custom PC in an old console (Atari 2600), and am struggling on how to make neat and clean looking ports for the HDMI, USB, and Ethernet wires to connect to. I think if I just cut holes in the console and stick the wires into them, it will look pretty ugly.
Both are pretty shoddy really. The second picture used three different methods, including some automotive/industrial AMP connector shells, dremel, and modified banana plug receptacles. You can also buy a lot of prefab parts that eliminate human error by being wider then the holes you bolt them on to.
Here is what I use generally when making custom devices.