薄 is built from the 艹 (grass (top)), 氵 (water (left)), and 専 components.
It belongs to a phonetic family with 博 and 縛 — they share the 専 component and the reading ハク.
A common word using 薄 is 薄い (うすい), meaning “thin, weak”.
Don't confuse it with 専, 博, and 縛.