I thought this was going to be a knitting blog, but it seems I have spent more time writing about the Depression so here is a bit of knitting stuff.
I make a lot of socks. and for years I picked up the stitches along the heel flap as directed then picked up the strand of yarn that ran between the first and second needles, knit into the back of it to twist it and avoid a hole. I did the same on the other side between the second and third needle. Sometimes it worked, but usually I still had a hole on one side or the other. I found, however, by picking up the stitch in the row below the first stitch on the second needle and knitting into the back of that, then repeating on the other side I never have a hole. This leaves you with one more stitch on the needle than the pattern calls for. If you are supposed to have 14 heel flap stitches, you now have 15. Knit one more row to set up for the gusset decreases. Knit the heel stitches, then knit in the back of the picked up heel flap stitches until you come to the last two stitches. Do not knit into the back of these stitches. Just knit the two off together as one stitch. Knit across the stitches on the second needle. Knit the first two stitches on the third needle together then knit into the back of the remaining heel flap stitches, then knit the remaining heel stitches. Now you are set up to start the gusset decreases.
Another thing that I find sock knitters question is how long to make the heel flap. Knit as many rows as you have stitches. If you have twenty four stitches on the needle for the heel flap, knit twenty four rows. This will give you enough depth that your heel will settle nicely into the sock heel and not pull down in the back.