This is easiest to work before binding off, but can be done after.
First Gathering Yarn 1 Use a piece of waste yarn or garment yarn (if you want to leave it in after seaming) threaded into a tapestry needle. Leave at least a 6″ / 15.2 cm tail, with a marker tied to the end so it doesn’t pull through.
First Row of Gathering Yarn 1 Begin by bringing the tapestry needle (TN) and yarn up from the WS into the center of the stitch before the first BO stitch marker; take the TN down in the next stitch to the WS (the stitch on the other side of the marker). *Skip one stitch and bring the TN up into the next stitch. Skip a stitch and take the TN down in the next stitch. Repeat from * across to one stitch before the second BO marker. Take the TN to the WS in the stitch following the marker. Cut the yarn and tie another marker in that end.
Setup Gathering Yarn 2 With the RS of the Front facing you, add marker and leave tail as for Yarn 1.
Second Row of Gathering Yarn Begin by bringing the TN and yarn up from the WS into the center of the stitch before the marker as before. Take the TN down into the second stitch from the marker, *skip one stitch and bring the TN up in the next stitch. Skip a stitch and bring the TN down in the next stitch. Repeat from * across to come up in the the last stitch before the BO marker. Take the TN to the WS in the stitch following the marker. Cut the yarn and tie another marker in that end.

