If you want a longer leg section, continue in this same manner,
changing the purl (background) then the knit (cable) colour every two or
three pattern repeats, changing only one of the colours at any one
time til you get the length you want, ending with the last row of a
pattern repeat. It's important to end at a point when you're about to
change the background colour. Break that strand as usual.
Leave the strand you've been using for the knitted sts attached to the
sock - you'll need it later. If you must cut it later because you need
that colour for your heel flap, leave a length a foot or so long.
I worked the heel flap on 22 sts (it will be a multiple of 3, plus one
st, ie 19, 22, 25, 28). The heel flap should be centred on the pattern
sts so that a purl st sits below the very first and very last st of the
heel flap. Place the remaining (instep) stitches on a spare needle or
stitch holder for now.
Work back and forth in stocking st, alternating the colours worked for
each stitch, working each st in the opposite colour of the one below it,
changing one of the colours every 4 to 8 rows for desired heel flap
length (I worked 20 rows). End ready to work a right side row.
Work your favourite heel turning, still changing one and then the other
of the colours every 4 rows as needed. Be sure your last colour change
introduces the colour last used for the cable sts on the instep. (Note
how many stitches you end with when finished turning the heel.)
If you've worked only one or two rows of your current colour
combination, continue with it. If you've worked 3 or 4 rows, you'll
change one of the colours. One strand (matching the cable sts on the
instep) will be the cable colour, change the other one to the new
background colour.
Work across the heel sts, alternating colours as established on
the heel.
With background colour, pick up sts along the side of the heel flap,
make 1 stitch right before your instep sts. Work across the purl
instep stitches only, slipping the knit sts as needed. Make 1 st right
after the instep stitches, pick up sts along other side of heel flap.
Knit across half the number of heel sts you ended with, alternating colours
for each st. Your round now begins at the centre back of the sock.
Working on the instep stitches only, from the wrong side (inside) of
the sock, pick up the yarn you used for the cables. Slipping the
background stitches as you encounter them, purl the cable stitches all
across the instep. Break this yarn. My apologies to those using a
circular needle, you'll need to slip some sts during this manouveur.
Now, you need to rearrange your stitches. If using 4 ndls, on
the second needle, there should be your original cables (I had 6) with a
purl st between each, plus 4 extra sts in the background colour at each
end of the ndl (I had 25). Half of the heel sts plus the rest of the
picked up gusset sts should be on each of ndl 1 and ndl 3.
Note: If using a circular needle, place markers where the ndl
changes would be. If using 5 ndls, arrange as you see fit, keeping instep
sts together, and using markers if needed.
Work across the first needle, alternating colours with every stitch.
On ndl 2, p1 with background colour, k2 with cable colour, p1 with
background colour. Then continue to work in the pattern as already
established on the instep sts til you reach the last 4 sts on ndl. P1
with background colour, k2 with cable colour, p1 with background colour.
You now have 2 more cables set up (I had 8). Work ndl 3 the same as ndl 1.
You'll continue to work cable pattern as established, with colour
changes every 8 or 12 rounds (2-3 pattern repeats) on the instep sts.
You'll continue to work the sole by alternating colours so the new st is
not the same colour as the one on the row below it.
Work another round or 2, then begin working k2tog decreases one
stitch before the end of ndl 1 and an ssk decrease on sts 2 and 3
on ndl 3.
Work the decreases every round or every second round as needed
to fit your foot. Then continue to knit without decreasing, continuing
in patterns established.
When about 1.5-2 inches short of desired foot length, work 1 complete
round in sole pattern. If total number of sts is odd, k2tog at one end of
ndl 2 on this first round. Work another round or 2 without decreasing.
Finish up with your favourite toe shaping, cut yarn and close toe.
As noted above, there are a couple of ways to make this sock larger.
The first is to add extra pattern repeats, ie cast on a larger number of
sts. The other is to use a thicker yarn, ie worsted instead of dk, etc.
Naturally, for a smaller sock you'd cast on fewer sts or use thinner yarn,
such as sport or fingering.
Estimating yarn amounts can be difficult. The dk I used most for this
sock has 124 metres per 50 gram ball. One sock, with 5.5 inches worked
before the heel flap, checks in at about 75 grams, so this pair used about
372 metres in DK. The same size pair in worsted would take fewer metres
(but probably more grams), and in sport would take more metres (but
probably fewer grams).
If you're mixing yarns, it's important to note the care requirements
for each of them. You'll need to launder the socks according to the
fussiest yarn's requirements.