Here are the instructions for the original Shoo Fly Block.
http://4.bp.blogspot.com/-zmQNIaO4Ri...nal_Page_1.jpg
Some of the corners have QST's on them to produce the shading effect. This is for a Ohio Star but it shows clearly how to make the QST's.
https://www.thesprucecrafts.com/easy...-units-2821468 You only need them on half of the corner blocks.
I have been looking for a quilt pattern for my granddaughter. It has to feature horse fabrics. I started with your focus quilt and then added borders to make it big enough for her to snuggle under. The finished Shoo Fly Blocks are 15 inches. I really like my 80x88 version from EQ7. fyi....her favorite color is teal.
Edited to add: I added the rotary cutting for the 15 inch finished (15.5 before it's sewn together with the other blocks) to show you what the QST cornered blocks look like.