procrastinate, dilly dally
蹭 centers on moving slowly and hesitantly, wasting time instead of acting directly. The given meanings of procrastinating and dilly-dallying both express this idea of sluggish, reluctant motion.
蹭 combines 足 (foot) with 曾, which likely contributes the sound. The character suggests hesitant, shuffling foot movement, fitting the idea of procrastination or dawdling.
The left side is 足 (foot), and the right side 曾 looks like a layered, complicated structure. Imagine your feet getting tangled in layers of hesitation, making you shuffle and procrastinate instead of walking briskly.
For ソウ, picture someone procrastinating so much that they end up sewing (ソウ) their own feet to the floor: sew -> ソウ, and the foot radical 足 ties it all together.