trample on, tread on, walk on
踖 centers on the action of stepping heavily or walking over something, conveying trampling, treading, or walking on a surface with force.
踖 combines 足 (foot) with 昔, which likely contributes the sound. The character expresses actions done with the foot, such as trampling or treading.
The left side is the foot radical 足, and the right side is 昔 (old times). Imagine an old foot stomping heavily on the ground, trampling everything in its path.
For セキ, picture a foot trampling on a stack of old newspapers, making a loud 'seki' sound with each step: seki -> セキ.