Buildable Foundations?

First off, thank you very much to all the dedicated modders out there! You have breathed new life into my game (particularly Outposts). I'm just wondering if there are any buildable foundations that you can build Outpost structures on. Sort of like terrain but concrete so you can have a solid (flat) foundation to build on. I want to build an Outpost on a smooth flat surface and maybe give it some roadways to drive around my Outposts.