Granny square afghans, with their colourful rounds of double crochet stitches, are a standard among crocheters. Each individual motif is created separately, then joined together to form the desired size afghan. The final step in creating a granny square afghan is crocheting an edging around the entire assembled afghan, giving the piece a uniform and finished appearance. Traditionally, the edging maintains the same double-crocheted clusters and spacing used in crocheting the motifs. While this edging isn't difficult to accomplish, creating a ripple-free edging that allows the afghan to lie flat without blocking requires a bit of attention and care where the individual motifs are joined together.
Insert the crochet hook in the corner space in any corner of the afghan, leaving a 6-inch tail. Pull up one loop, draw the yarn through the loop on the hook and chain three. Insert the hook back into the same three-chain corner space and make two double crochet stitches in the same three-chain corner space. Chain one. Do not turn your work.
Make three double crochet stitches in the next chain space between the double crochet clusters in the motif, creating one cluster. Chain one. Continue working in this established manner, working three double crochets between the double crochet clusters in the motifs and crocheting one chain between clusters. Work across the first motif until reaching the corner spaces between that motif and the motif to its left. Chain one before the corner space of the motif.
Make one double crochet in the corner space of the adjacent motif. The next stitch deviates from the three double-crochet cluster by creating a stitch called a dc2tog, or crocheting two double crochets together. Yarn over the hook, insert the hook into the corner space of the first motif, draw up one loop. There will be three loops on the hook.
Yarn over the hook and draw the yarn through two loops on the hook. Yarn over again and insert the hook into the corner space of the next motif to the left. Yarn over and pull the yarn through all three loops on the hook, leaving one loop on the hook. The double crochet two together stitch (dc2tog) is complete. Chain one.
Continue in the established pattern across the side of the afghan, making one double crochet cluster in the spaces of the adjacent motif and one double crochet plus one dc2tog where two motifs join.
Work the corners of the afghan by crocheting one cluster of three double crochets in the first corner space, chain three and working another cluster of three double crochets in the same corner space. Resume the established pattern on the next side of the afghan.
Work in the established pattern around the entire afghan, working one double crochet plus one dc2tog where each motif joins its neighbour. When you reach the beginning of the edging row, join the yarn with a slip-stitch to the third chain of the chain three segment, which is part of the first double-crochet cluster.
Crochet as many rows of granny-square style double-crochet clusters edging as desired, omitting the dc2tog stitches from subsequent rows and crocheting regular double crochet clusters in every space from the preceding row. Fasten off the yarn when finished, and use a blunt tapestry needle to weave in the loose ends.
After completing the foundation edging row with the dc2tog stitches, following rows can be any combination of stitches you desire.
Use the same size crochet hook you used to create the motifs and maintain the same tension to create a uniform look to the afghan.