Some sock knitters feel a little overwhelmed when it's time to pick up the gusset stitches on the side of a sock heel. It feels magical because you're basically creating something from nothing. There's no reason to panic, though.
Picking up gusset stitches is a lot easier if you do some preparation when you're knitting the heel flap of your sock. Just slip the first stitch of every row of the flap. Slipping that first stitch creates a neat column of elongated stitches along the flap edges. It also decreases the number of edge stitches. You end up with one edge stitch for every two rows.
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