I would sit down with graph paper and "lay" the blocks out that way. You can add filler strips and smaller block designs to fill in the larger spaces. You can make mini 9 patches, checkerboard strips, mini friendship stars, flying geese strips in several sizes, etc, etc to fill out a design and it'll be far more interesting and look like it's supposed to be that way instead of the "just sash them all to the same size" method.