When you do the rows after the ribbing where you slip the first stitch of every new row, are you just making a rectangular shape with slipped end stitches? I’m used to toe up socks, so Im a little confused.
That’s exactly what you’re doing. Actually, I think you just make a square, but be sure to slip the first stiches 
Thanks so much!
Yep, it’s the heel flap, and it should work out to be pretty much a square.
Sometimes the heel flap knit row can be sl 1, k1, sl1, k1 right across the row with the purl row being sl1, purl to end of needle. This makes a nice reinforced heel.
JudyD