Each row is made up of 6 blocks. 4 block that are the same form the illusion of the big block. The first row of the quilt in the pattern picture is made up of 2 brown, 2 green, 2 blue. The second row is 2 brown, 1 blue, 1 green, 2 blue. That creates the illusion the first large brown block is on top of the blue block and the blue block is on top of the green block.
Wow! That sounds more complicated than it should. I hope you can look at the pattern picture and sort of follow what I'm saying.