Notes:

120 g (60 g per sock or per colour)
foot: 24.5 cm; leg: 13.5 cm

I am knitting these as reversible double-knits. Just to see if that can be done.

I started the cuff with a provisional cast on, knit approx 15 rows in white, 3 rows in blue, 3 rows in white, approx 15 rows in blue.
Then I picked up the stitches from the provisional cast on and folded the cuff, ready to start the double knitting.

The pattern advised to increase stitches here but since double knitting has more stretch than stranded knitting I kept my stitch count at 72 stitches (a bit too much but reducing the pattern by one pattern repeat would have been too tight).

After 3 pattern repeats I started the heel flap over 36 stitches. Two more pattern repeats back and forth just like any other heel flap. Just that this one has two layers. I separated the layers for the heel turn. I’m sure there’s a more elegant way but I didn’t have the patience to look for one…
One heel turn in white, the other one in blue.

After the heel turns I reunited the 22 remaining heel stitches on one needle and picked up twice as many stitches as usual on the sides of the flap. These stitches got incorporated alternately into the outer or the inner layer.

I placed markers between the heel stitches and the picked up stitches. That’s where I placed the gusset decreases (at the end of the heel flap and not between the picked up stitches and the instep) so that I could continue the instep pattern uninterrupted on the gussets.

The stitch count on the sole stayed at 22 stitches. I skipped the striped pattern of the stranded version and did the sole in plain white and plain blue.

I improvised on the toe decreases. When the foot of the socks seemed to be long enough I started symmetrical double decreases on the outside and the inside so that there is one central stitch into which all the other stitches are incorporated. In the end I grafted the remaining stitches. First the inner stitches and then the outer ones.