Stretch the fabric in a hoop.
Then make a cross.
Change to another thread and come up in the centre, between two of the arms of the cross.
Take the needle underneath the arm behind and the one in front, thereby whipping one arm.
Don't pick up any of the fabric.
Continue your way around the cross, taking the needle underneath two arms.
For the last stitch, whip only the arm behind the needle, and then
anchor the stitch underneath the diamond of blue thread.
Read more about this stitch at Sarah's Hand Embroidery Tutorials .
Pumora has made an interesting alternative embroidery stitch.
At Layers of Learning you can read about the original God's Eye, Ojo de Dios, and how to make such an object out of sticks and yarn.
SSS Reference Chart
Teal Wool Tailoring Scribble Cloth