These puzzles make use of a technique of meshing LEGO panel pieces together. The instructions provided are for a basic square version but the technique can be extended to build puzzles of any size. The complexity can also be varied by changing the number of separate puzzle pieces, as pictured below.
This technique could also be used to create patterns that represent interlocking bricks or tiles in other models.
Note that this only works with the older version of these panel pieces.