I usually look at the foundation paper as a finished block and then de-construct it. In the case of Block A, you need two HST's of each colour that finish at 2 3/4 inches. I would cut my squares 4 inches (to be safe) and then cut diagonally for the 4 pieces that are needed. Block C is similar but with one square left whole. Block D needs two more of those same sized HST's and needs a strip of fabric in the center, that measures 2 inches in diameter (I would cut that strip 2 3/4 inches just for a little safety)
And I would continue on with the measurements, perhaps only cutting one strip of each to begin with, just to make sure that I had the correct dimensions. Pretty pattern. I am looking forward to seeing the finished product.