TRY MATTRESS STITCH
Place your knitted pieces right-sides up, side by side. Thread your yarn on to a needle, anchor the end and weave along an edge to your start point. Working from back to front, push your needle up between the first and second stitches of the left piece’s edge, then insert the needle down between the first two stitches of the right piece’s edge (on the equivalent row). Moving upwards, bring the needle back up on the right piece, scooping up the bar that lies at the back of the stitch. Return to the opposite piece and repeat.