Do you mean the bottom right corner of the photo? It looks like damage, not an intentional piecing choice (unless that corner is explicitly cut - maybe to piece in a triangle to complete it, then create a square/diamond where 4 of those blocks would come together?)
I'm sorry, the picture is not the best. This is a stack of the blocks, so you are seeing pieces of the blocks that are below this one. The blocks are square, made somewhat scrappy, but mostly the same colors in each block.