I would divide into 16 units, and sew all pairs together, then into a 4-patch, then into 4-patch again , then the one big 4-patch, pressing seams so they nest together. I usually have a plan, which way I need to press my seams so they nest together nicely, before I start sewing. I like to cut the threads when string piecing, and arrange them between each set of chain piecing, using a leader and ender between each line of chain piecing.