Without mods or messing with your config files there are items you can spawn in console commands that will give you (blue) foundation in mid air. one is a mine-able stone pile, and my favorite is goblinking_totemholder.
the totemholder you cannot break or deconstruct, so if you place it incorrectly, you need to use a command to delete it.
I use "forcedelete radius=1 goblinking_totemholder"
This trick has allowed me to make towers that reach the clouds and stadium sized buildings without mods or editing files.
Check out my screenshots for a few examples.