chimney
囱 centers on a chimney: a vertical passage for smoke to escape from a fire.
囱 is a pictograph of a chimney or window opening, with the modern form retaining a framed opening and inner strokes suggesting smoke or structure.
The outer 囗 is the chimney opening, and the inner 夂 looks like smoke curling upward. Together, 囱 is a chimney.
For ソウ, imagine a chimney soot-covered and old: soot -> ソウ, and the smoke rises through the chimney.