How do I make custom maps?

[Silent Sorrow]

In another thread about empire placement someone said the way to guarantee even empire placement throughout the quadrant was to make your own maps, place the empires manually and then give that map to someone else who thus wouldn't know exactly where those other empires were.

Sounds like a good idea.

Question: How the hell do I do that?

I don't see anything in the game when I load it up that indicates I can do this. And I've checked the FAQ and the modding tutorial as well.