Easy Puzzle
I think I've proven that the only solutions involve the pawns in exactly that position (and none is promoted, the knights are at the corner, and the rooks are next to the knights. The remaining four pieces can be distributed in any way (as long as the bishops are of opposite colors, of course). Those knights are so hard to block.
Like I said its only a handful of solutions. I teach people to play chess and this one is one that I've found very helpful in teaching beginners how pieces move because it forces them to think about more than one thing at a time. I'm by no means a brilliant chess player but I teach people the basics and that's pretty much it.
Here's a quick minute puzzle for anyone who wants it! :) 1. Remove all of Black's pieces. 2. Arrange all of White's pieces so that White can make no legal moves. 3. You MUST use all of White's pieces! 4. The pawns cannot be on their "Queening" square. There are a handful of solutions to this!