While I wholeheartedly agree about the joy of sticks, boxes, twine and above all dirt -- there is a glaring omission from his most excellent article:
Tape. And lots of it. Case in point:
Claire's version of London Bridge. Constructed completely on her own in a quiet hour which I used to whip up a 30 minute Rachael Ray dish (really, don't these always take like 20 minutes longer than they should?).
The bridge hung on until this morning when her bouncing turtle finally shook it from the couch.
So I say hand over a roll of tape to your little one, see where it takes them! It's cheap, easy to clean up and there's probably a half dozen rolls stashed in your junk drawer as you're reading this.
Messy bedhead hair is of course optional, but I feel it adds to the experience.