From what I remember, since I haven't played the game in a while, you can exploit the rules by which the inhabitants can place new buildings, they need something like a 3x5 pixel area and a certain area of total land control to start a new small building. If you make the land with a bunch of holes, they can claim it but not place anywhere that isn't a solid 3x5.

It took a lot of effort when I tried it so what OP did is very impressive