From the pictures of that quilt, I still am not seeing that the sashing was created from separate half square blocks but I am thinking that's the only "easy" way to get those in there. Doing the sashing the length of the original block and putting triangles on the ends would be so confusing to get it all coordinated, even though it would certainly cut down on the bulk of the extra seams. If anyone finds an easy way to do that, please speak up.
It would work if all of the sashing triangles and cornerstones were the same (Jenny Doan's method) but not if you want them all different as in the example. Am I correct?