Regia Uni 4ply one ball blue (Colour A), one ball green (Colour B)
Any other 4ply sock yarn in contrasting colours would work.
To fit UK size 7 (European 41)
8sts to the inch
CO 60 sts, K2 P2 rib for 1 inch in Colour A
Knit one round in Colour A , then one in Colour B, continue in stockinette stitch striping in this manner, always picking up the new colour strand from under the old one at the end of each round/stripe (jogless stripe). Continue until leg is 6inches long or desired length ending with a stripe in the same colour as the cuff/heel/toe. Turn and purl across 30 stitches, leave the other 30 stitches on their needles or a stitch holder as preferred (these will become the instep stitches).Heel flap:Using the stitches just purled work heel flap as follows:
Row 1: *Slip 1 purlwise, K1*, repeat across the row
Row 2: Slip 1 purlwise, P to the end of the row
Repeat these two rows 14 times (30 rows worked total)
Row 1: (RS) S1, K16, SSK, K1, turn
Row 2: (WS) S1, P5, P2tog, P1, turn
Row 3: S1, K6, SSK, K1, turn
Row 4: S1, P7, P2tog, P1 turn
Repeat these last two rows, working until the last stitch before the gap each time, until there are no more stitches to be worked
Turn and knit across the heel stitches
Pick up and knit 18 stitches along the side of the heel flap (approximately one per row plus one or two more in the gaps between the needles and the flap, don't worry about being too exact as numbers can always be evened up during the gusset decreases). You may wish to knit the stitches through the back loop. Knit across the instep stitches then pick up and knit 18 stitches along the other side of the heel flap.
At this point rearrange 9 of the heel stitches from the first needle to the last one. There should be 27 stitches on the first needle, 30 instep stitches on the second needle1 and 27 heel stitches on the last needle. The start of the new round would usually be between the two needles of heel stitches.
However, due to the 'seam' formed when changing colours in the striping, which would be uncomfortable to have underfoot, the round is going to start at the beginning of the instep stitches. Therefore, when the stitches have been arranged on the needles knit across the remainder of the heel stitches in the colour you used for the heel. Add in the next colour for the new round and proceed as follows, changing colour each round as before and beginning the round at the beginning of the instep stitches.
Round 1: Ndl 11 K, Ndl 2 K1, SSK, K to end of Ndl, Ndl 3 K to last 3 sts, K2tog, K1
Round 2: Knit all stitches
Continue knitting foot until it is 1.5inches shorter than the length of your foot. I am a UK size 7 and my foot is 10inches long, if that helps to give guidance. End with a round of the contrast colour, cut that thread and continue in the colour used for the ribbing and heel.
Round 1: knit
Round 2: (keeping the needle numbering used for the heel gussets) Ndl 1 K1, SSK, K to last 3 stitches, K2tog, K1; Ndl 2 K1 SSK, K to end of Ndl, Ndl 3 K to last 3 sts, K2tog, K1
Repeat these two rounds until 32 stitches remain. Repeat Round 2 twice more (24 stitches remain), slip stitches from needle 3 onto needle 2, graft remaining stitches together. Sew in ends. Try on finished sock. Immediately start on sock 2 to prevent the onset of “second sock syndrome”.
Begin with Colour B and use that for the cuff, heel and toe, with stripes in between as in the other sock.