Creating a map from custom settings
Sometimes it's useful to create a new game with map and/or map generator settings stored in a JSON file rather than going through the in-game map settings screen. One reason is that by editing the settings directly you can get settings outside the range normally available from the GUI.
To do this you'll need to be able to run Factorio from the command-line, a JSON file containing your map generator settings (if customizing them), and/or a JSON file containing map settings (again, if you want to customize them).
For example, let's make a map using these custom generator settings: