dwarf
矬 centers on a person of unusually short stature: a dwarf. The meaning is specific and concrete, with no clear abstract extensions from the given gloss.
矬 combines 矢 (arrow) and 坐 (sit). The exact historical origin is uncertain, but it likely uses 矢 to suggest shortness (arrows are short compared to a person) and 坐 to reinforce a low or seated posture, together indicating a dwarf.
An arrow 矢 sitting 坐 down: imagine a very short person, like a dwarf, whose height is no taller than a seated arrow.
For サ, picture a dwarf sitting under a small sapling: sapling -> サ, and the dwarf rests beside it.