Love the Octagonal base, but hate having to dig up all that iron before building your base? Need something a little more simplistic that can be changed later on? This base is good for those early in the story or adventure game. It only requires marble, glass, and limestone, yet has plenty of room for improvements and modification. A steel or similarly tough shell can be applied to the outside for better defense later. These can also be linked together for a larger base, like the Octagonal base.
I would like to credit the creator of the octagonal base for some of my design inspiration. Note: this base is not square. If you want to modify it to be square, feel free. :)