Great pictures - self explanatory!
I recently saw a block like this with one more step.
They took a charm square the size of the pieces after you cut the 9patch horizontally and vertically (into 4 pieces).
They drew a diagonal line - sewed 1/4" on each side of the line - cut on the diagonal line.
http://lynbrown.com/wp-content/uploa...Gen-Quilt2.pdf
It 'looks' like it's complicated to make but the directions look easy to make.