I like to figure out the puzzles on my own, even the bonus puzzles, because there's generally enough information present to do so. However, this one has me stumped, so I checked Roeland's map. Even after that, I still can't see the clues that indicate which squares should have the stones. Those squares look the same as their neighbors.
Can anyone enlighten me? (Again, I HAVE the solution, I just want to know WHY this is the solution.)