How long should the heel flap be?
Continue working the heel flap in your preferred manner until it is about 2-1/2″ to 3″ long, depending on the wearer’s foot size. End with a right side row.
What is a gusset stitch?
Generally speaking, one stitch is picked up along the edge of the heel for every two rows of knitting. So, if you’ve slipped the first stitch of every heel flap row, you just pick up one new stitch in every edge stitch.