Ok, this post is going to have a lot of pictures because I'm just not too good at explaining what I'm doing. It's easier for me to just show you...and hopefully that will be more helpful for you, as well. :)
To start this style, I parted Syd's hair from ear to ear and cornrowed the back half of her hair straight down.
After this, I parted out a large square on the top of her head. I put a cornrow straight across the front and tied both sides out of the way for now.
I parted out a triangle in the front left corner of this square. I didn't do anything with this triangle yet - I just tied it out of the way until later.
Then I made a cornrow next to that triangle. After that cornrow, I parted out another strip of hair and tied it out of the way until later.
I continued this pattern as I moved diagonally from the front left to the back right corner of the square. You are basically making parallel parts but only cornrowing every other section of hair. I had 4 cornrows and 5 strips of loose hair when I finished.
Next I moved to the front right corner of the square. I parted the hair (moving over the previously made cornrows) to make a cornrow that crosses over the cornrows that were already there.
I did the same thing next to the cornrow I just made. You will have a strip of hair that has a few cornrows running through it. Cornrow the strip of hair you just parted out. When you move over the earlier cornrows, you'll have to do a couple stitches where you don't add any hair.
When you've moved all the way to the back of the square, you should have a pattern that looks like this:
Now it's time to move over to those side sections. This is the shape of the section of hair I was left with after I made the square.
I wanted to do two criss cross cornrows on each side, so I split this section in fourths, parting in half horizontally and then vertically.
Repeat that with the hair on the other side and you're done!