I have now enabled the flatlands – a flat land (duh!) where you can use creative mode! This is however only available to people with a free lot! So if you are settler, you have to choose between EITHER an empire lot OR a flatlands lot. The number of maximum lots is not increased for anyone!
In order to get a flatlands lot, please look at this map here, choose a lot and then go the the “Become a settler” page to choose a lot!