The right side of the skirt the design is being sewn on. The short stitches of black thread are forming the guiding lines of the pattern on there, a bit messy looking but fully visible without any kind of pencil marking, and not shifting.
https://eldritchcafe.files.fedi.monster/media_attachments/files/115/611/478/555/928/046/original/fce35228e3eccc83.jpg