Chain four. Join the ends with a slip stitch to make a loop. Chain three. This will count as the first double crochet stitch in the first cluster of each round. Do two double crochet stitches in the center loop. This is a beginning cluster stitch. Chain three. Do three double crochet stitches in the loop. This is the typical cluster that is used throughout the granny square. Chain three, and then crochet a cluster of three double crochet stitches in the loop. Chain three, and then crochet a fourth and final cluster. Chain three. Slip stitch in the top of the beginning stitch to complete the first row.
Slip stitch across the two double crochet stitches in the first cluster of the first row, then chain three. Make a beginning cluster in the same space. Chain three and crochet another cluster in the same space. Every beginning corner will be worked in this manner. Chain one. Continue working around the second row of the square, placing two clusters in each corner, separated by three chain stitches. The clusters on the sides of the square are separated by one chain stitch throughout this project.
Crochet a beginning cluster in the corner chain-three space of the third row. Chain three, then crochet another cluster in the same chain-three space. All consecutive rows will be worked in the same manner as the third row. Around the edge of the granny square, you will have clusters of three double crochet stitches with one chain stitch between each cluster. Crochet a cluster in each edge space between clusters. Chain one. Continue until you reach the corner. Do a cluster in the corner, chain three, and then do another cluster in the corner.
Continue working around the edge of the blanket in concentric rounds until the granny square reaches the desired size. Cut the yarn about 4 inches from the hook. Tie-off and weave-in loose ends.