http://forum.paradoxplaza.com/forum/content.php?2103-EU4-El-Dorado-Development-Diary-2-The-Nation-Designer

Welcome to the second development diary for Europa Universalis 4: El Dorado. Today we’ll only be talking about a single feature, but it’s probably the single biggest feature we’ve added to EU4 since launch: The Nation Designer.

As the name implies, the Nation Designer allows players with the El Dorado expansion to create their own, custom-designed nation to play instead of picking one of the historical nations. The Nation Designer is available for both Single-Player and Multi-Player, and can be used at any start date as long as you are starting a new game.

To make a custom nation, you simply click the new ‘Custom Nation’ button during country selection. This will prompt you to pick a capital province for your custom nation: Choose carefully, as the capital province cannot be changed without cancelling your custom nation entirely! You can start anywhere on the map that isn’t water or wasteland.