Very similar to puzzle 11, this one requires a level of comfort with your dog pawing at it, in order to get the pieces to fall into different pickets. This one, however, also comes with pockets where you can hide treats and your dog has to nudge the lid to uncover them, separately from the pushing game at the center.

Just like with most puzzles, the fewer food/treat pieces you have your dog work for at a time, the better. That way their success is based on their skill set, rather than a high probability of multiple pieces being everywhere.