This block has quite a few 1/2 square triangles along the edge. I really didn't want to leave the square with all sorts of biased edges exposed. So, I made the corner blocks using the regular formula for 1/2 square triangles but, for the edges, I cut 1/4 square triangles. To make them large enough, I measured the short side of the triangle and added 1 3/4" inches to the measurement to get my measurement for the square. Then I cut the square into 4 triangles as shown below.
Here is the block laid out and ready to go. I've done the 1/2 square triangles for the centre pinwheel.
Once I completed the centre pinwheel, I approached this block as a little mini quilt set on point. First I created strips. The trick here is to pay attention to your pressing. I made sure I pressed away from the pinwheel (to minimize bulk) and then made sure for each row I alternated the direction of my seams.
I then sewed the strips together. Then I added the corner triangles. I left them to last just because I like to. There is no real reason they couldn't have been done as part of the strips.