step on
躡 centers on the physical act of stepping on or treading upon something.
躡 combines 足 (foot) with 聶, which likely contributes the sound and relates to stepping or treading.
The left side 足 means foot, and the right side 聶 looks like three ears stacked. Imagine a foot stepping on a pile of ears to remember the meaning 'step on'.
For ジョウ, imagine stepping on a soft 'jelly' dough: jelly -> ジョウ, and your foot sinks in as you step.