The amount of yarn originally specified in the pattern (100 grams, which is 1 ball), is not enough to make the slippers. I was able to finish one and get about halfway through the second before running out of yarn. You definitely need 2 skeins. The 2nd-to-last photo shows how far I got with 1 skein - one slipper, plus the leg of the second. ETA: The pattern has now been corrected to show 200 grams of yarn needed for all sizes.

I used part of a different skein to finish - I ripped out the toe that had already been done, and used that to make the flaps for the second slipper. Then I used the yarn from the other colorway to knit the foot/toe of both.

Even though I’ve made a lot of Drops patterns, I found this one to be a little harder than usual to understand. I think it would have helped to have a schematic. But part of the problem was just not understanding what they meant by “middle” parts - those are the overlapping flaps on the front of the leg.

Construction:

The slipper is knit by casting on stitches along what will become the seam running vertically up he back of the heel/leg. The right and left edges of the piece will become the top edges of the cuff after the fabric is folded in half and seamed, with the folded edge being under the heel.

The pieces that are called “middle part on top” and “middle part under” are the flaps on the cuff of the leg. The pattern has you work the “on top” one first, then the front of the foot before doing the second flap. This way, the flap that goes on the outside matches the color at the beginning of the foot/toe section (which is the middle of the foot). It doesn’t matter if the “middle part under” has an abrupt color change, since you don’t see it anyway.

The foot from the instep to toe is knit on the center section of stitches, and joined to be worked in the round. This section must be a multiple of 3 stitches for the rib pattern.

I drew a chart that might be useful as a schematic.

For the toe decreases, the pattern just tells you to decrease in the 2-stitch purl sections of the rib, but it’s left up to you to figure out how to do that fairly evenly. There may be a more symmetrical way to do it, but this is how I did mine:

There are 13 purl sections in the ribbing (for the women’s small - the one with 71 st cast-on).

1st decrease round (3 sts): decrease in the 1st, 5th, and 8th purl sections.

2nd dec (2 sts): dec in the 4th and 11th sections

3rd dec (4 sts), dec in 3rd, 7th, 10th, and 13th sections

4th dec (4 sts): dec in 2nd, 6th, 9th, and 12th sections

After the decrease section, the pattern says “K 1 round. * Then K sts tog 2 by 2 *, repeat from *-* 1 more time”. I did the first round in pattern (k1, p1 rib), rather than all knit. And if it isn’t clear, the “K sts tog 2 by 2” means to k2tog around. If there are an odd number of stitches in the round, just knit the last stitch.

Note: The buttons are just decorative - they are sewn through both layers of fabric to hold the flaps in place. You could make buttonholes towards the end of each flap section to make them functional, but they might have a tendency to open up as you walk. Might be interesting to try it, though.