After you sew the stars blocks, you trim them down to 9.5" square. I have not done that yet, since my square ruler is in the mountains (I think...will have to look this weekend.)
This is meant to be a Fat Quarter pattern. You cut strips from each fat quarter, then subdivide to make both squares and rectangles. The longer strips will form a sort of double sashing around each block. I have not sewn the sashing strips yet, just placed them around the stars to get an idea how the top will look.