...and then add the last light gray unit. You will still have one
partially un-sewn seam. To sew that...fold the block right sides
together so that the un-sewn parts are aligned. Insert your
machine needle at the 1/4" seam line point where you stopped
sewing the first seam. Stitch, then backstitch one stitch to
hold the beginning of the seam, and stitch out to the edge.
Voila! One Crow's Beak block!