I'm what my DH calls "large-ish" so I make a bigger sock with 68-72 stitches on the leg and knit my heel flap about 35 rows to give me 17 stitches and decrease back to 68 and my socks fit me fine-jadancey said:
You might want to start with more stitches if the leg is too tight or make a longer heel flap if your instep is high.