seam
緎 centers on the line where two pieces of fabric are joined: a seam. The meaning is narrow and concrete, referring to the stitched connection itself.
緎 combines 糸 (thread) with 或, which likely contributes a phonetic element. The character is rare, and the exact historical development of the phonetic component is uncertain.
The thread radical 糸 on the left suggests stitching, and the right side 或 looks like a boundary or enclosed area. Picture thread running along the edge of fabric, creating a seam that holds the pieces together.
For ヨク, imagine a tailor carefully sewing a seam and saying 'yoke' as they join the fabric: yoke -> ヨク, and the thread 糸 makes the seam strong.