My preferred method is knitting toe-up socks - and ever since I first tried it, a flap heel.
I used the method described here, i.e. Sarah Keller's Generic Toe-Up, Slip-Stitch Heel, Sock Formula, which worked brilliantly for me.
The stitch pattern that I used was as follows (very similar to my Osterspaziergang Socks):
Using a multiple of 4 stitches, the pattern consists of 6 rows.
Row 1: * k1, ssk, yo, k1 repeat from *
Rows 2 and 3: k all
Row 4: * k1, yo, k2tog, k1 repeat from *
Rows 5 and 6: k all
The yarn used here is called Regia Cotton Tutti Frutti Color, colorway 2423 Grapes - here's a link to the yarn's Ravelry page.