So, yea, we’ve all had that moment when we’ve placed a whole bunch of foundation pieces, only to realize that last piece we need is clipping something, hanging off a ledge, too far underground, etc…
So why not use sticks and twine or vines to essentially sketch the layout before building?
On the blueprint/code side, I’m thinking either a new 2x2 (or 4x4 or whatever) foundation block or perhaps a 2/3/4/whatever block long fence type foundation, that would only snap to other blocks of its type. These layout blocks would then either have no collision so real foundations could be placed inside, or maybe upgraded by placing a real foundation on them.
The no collision option might be easier to implement, and could also be used for decorative purposes (eg, marking a path or something).
Art-wise, it could be as simple as a branch or spike mesh at each corner (scaled to one foundation tall) with bits of rope/vine connecting them to delineate the top edges.