Using the white yarn, cast on 44(48) sts and divide them onto four needles, 11(12) sts each. *K2, p2*, repeat *–* to end of round.
Begin the lace pattern in the round on row 1 of chart I. Work the 4 st pattern repeat 11(12) times. Work rows 2–4 of the chart and then repeat rows 1–4 three times.
Knit 1 round, evenly increasing 1(2) sts on each needle = 48(56) sts.
Begin the colourwork pattern on row 1 of chart II. Work the 8 st pattern repeat 6(7) times. Work rows 2–36 of the chart.
Knit 1 round with the white yarn, evenly decreasing 1(2) sts on each needle = 44(48) sts. Now work another lace section as in the beginning.
Begin the heel flap: knit the sts on needle I onto needle IV = 22(24) sts. Leave the other sts on hold. Turn work and begin the reinforced st pattern:
Row 1: (WS) slip 1 st (yarn in back), purl to end of row. Turn work.
Row 2: (RS) *slip 1 st (yarn in back), k1*, repeat *–* to end of row. Turn work.
Repeat rows 1–2 a total of 11(12) times = 22(24) rows.
Work another WS row and begin turning the heel. Continue working the reinforced st pattern as established. Work until 8(9) sts remain at the left end of the heel flap. Work the skp decrease (= slip 1 st knitwise, k1, pass the slipped st over) and turn work. Slip 1 st, p6(6), p2tog. Turn work. Slip 1 st, work until 7(8) sts remain, skp. Continue in the same manner, decreasing sts at the sides with 8(8) sts in the middle. When only the middle sts remain, distribute the heel flap sts onto two needles, 4 sts each.
Using a free needle, pick up 11(12) sts from the left end of the heel flap + 1 st. Knit the picked-up sts through the back loop onto needle I. Knit the sts on needles II and III. Pick up 11(12) sts from the right end of the heel flap + 1 st from between the needles. Knit the picked-up sts through the back loop onto needle IV. 54(58) sts now on the needles.
Knit 1 round with white and work the gusset decreases: k2tog at the end of needle I, skp at the beginning of needle IV. Work stockinette st, alternating 1 round of blue with 2 rounds of white. Repeat the decreases as established on every other round until 44(48) sts remain, 11(12) sts per needle.
Size 34: When the sole measures 16 cm, decrease 1 st on each needle = 40 sts.
When the sole measures approx. 17(20) cm (including the heel) or the sock covers your fifth toe and you have last worked the blue round, work the rest of the sock with the white yarn.
At the same point begin the toe decreases: k2tog at the midpoint and end of each needle = 32(40) sts. Work 3(4) rounds without decreases, then repeat the decreases as established = 24(32) sts. Work 2(3) rounds without decreases and repeat the decreases = 16(24) sts. 1 less round without decreases after each decrease round. Continue in this manner until 8 sts remain.
Break the yarn, pull it through the sts and securely weave in.
Knit the other sock to match.
Lightly steam the socks.