Cast on the required number of stitches
Make sure the stitches are not twisted
Place a stitch marker on the right needle
Bring the first and last cast-on stitches together
Insert the right needle into the first cast-on stitch
Knit the first stitch and the last stitch together if needed for a seamless join
Pull the yarn snug to close the gap
Continue knitting in the round
Check the join after the first few stitches to ensure it is smooth