Left Click Macro
This video shows you how you can create a macro for your keyboard or mouse that will click the left mouse button very quickly to assist with spamming foundations. While you can certainly do this with mods, some people don't use mods or want to wait until the 1.0 release before trying mods. Also shown is a technique for placing foundations without the hologram rotating.
Foundation Holes AKA Walkway Snapping
In Update 4, the undocumented functionality of walkway snapping was implemented. Walkway snapping allows for many foundation alignment techniques such as "foundation holes", "pillar corners", "inner walls for quarter pipes".