The trick to this block, or any like it, is to make the most pieced section first -- in this case it would be the 9 patch, it has the most seams.
AFTER piecing the 9 patch measure it and cut your rectangles using that measurement for the long side of the rectangle that adjoins it. This way it is more likely to fit your 9 patch.
No matter how carefully you cut a fabric, the thread you use, the size of your 1/4" seam (+ or - three or four threads more than mine or 'hers' for instance?), the "hand" of your fabric (how thick/thin/dyed/"finished" it is) all will affect a seam size. So, it's really easier to make the most pieced sections of your quilt first, then measure to get the size of the next-to-it cut you'll need.
So many people cut everything out at one time, then start sewing. To me, and I teach this way, that can be a recipe for frustration and mis-matches. I try to eliminate as much frustration as I can in a class and in my own sewing life!
Jan in VA