Align the granny squares with right sides facing or as preferred
Use a yarn needle and matching yarn to whip stitch along the edges
Use slip stitch crochet through both loops of adjacent squares
Use single crochet join by crocheting through both squares’ edges
Use flat slip stitch join for a neat, low-profile seam
Use mattress stitch for an invisible sewn join
Use join-as-you-go while finishing the last round of each square
Pin or clip the squares in place before joining
Work from one corner to the next for consistent alignment
Weave in all yarn ends after joining