Place the pieces together with the wrong or right sides facing depending on whether you want your seam to be hidden on the wrong side or show on the right side of your work. Hold the pieces in your hand with the two edges facing you.
Insert the hook through both pieces at the beginning of the seam and pull up loop, chain 1. Work a row of single crochet by inserting your hook through both pieces at the same time. Complete the seam and secure the end of the seaming yarn.