there is one big rock in almost every pile......any significance to that?
It's called
the initiator rock in the directions ewest referenced. I mentally call it the headstone (headboard) of the SMB bed; I think it tells Mr. & Mrs. Smallie how to orient themselves, sort of.
I'll tell you how it had the most significance to me. Most of the initiator rocks are so big that I was the only one who could move them. So I placed them all ahead of time, added bulk portions of smaller rocks, and turned the kids loose to build as many SMB beds as they wanted
right where I wanted them to be.