Sew each row together. Press seams in one direction, alternating rows. Nest seams when joining rows.
I like to sew the top two rows together and the bottom two rows together. Then sew the center seam last. To reduce bulk in the center, you may wish to press this last seam open.
Make twelve blocks just like this one. In my case, half-pink and half-yellow. According to the pattern, half-light and half-dark.
Next make four more blocks using only your light fabric. Mine are all yellow, with no pink.