I modified the pattern for size S as the following:

• Started with 26 stitches (instead of 30), 13 per needle, and repeated increases up to 58 stitches, 29 each for the instep and the sole parts.

• Worked the given lace pattern, but stitches No.2 to No.30 only, for the instep part. (Sole stitches were all knit, as instructed)

• For the gusset section, increased sole stitches to 49 (The number of rounds in my gusset section is fewer than that in the given pattern by two rounds, so I started the gusset section when I came to the point which is about 7cm shorter than the total length)

• After finishing the heel flap, decreased two stitches evenly from the sole part just before restarting the lace pattern for the instep part --> now, sole stitches are 27 while instep stitches remain 29

• For the sole-side lace pattern, worked stitches No.3 to No.29 of the given lace pattern only

I wondered how the connection from the end of a round to the beginning of the next round in my modified lace pattern would look, but it seems OK. (See the second photo). Rather, the connection between instep lace stitches and all-knit sole stitches is a bit messy.

Anyway, I’m satisfied with my result.
Thank you so much for a nice pattern!