plough
耤 centers on the act of ploughing, specifically using a plough to turn soil.
耤 combines the plough radical 耒 with 昔, which likely contributes a phonetic element. The character is associated with ploughing, but the exact historical development is uncertain.
The left side 耒 is a plough, and the right side 昔 suggests something old or past. Picture an old-fashioned plough turning the soil.
For セキ, imagine a plough cutting through the earth with a sharp, quick motion: the sound 'seki' echoes the swift slice of the blade.