This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
宱 combines 宀 (roof) with 作 (make). The exact historical development is uncertain, and the character is rare with no established meaning.
The roof 宀 over 作 (make) suggests making something under a roof, but the kanji's meaning is unclear.
For サ, imagine a saw (サ) cutting wood under the roof 宀 to make (作) something: saw -> サ.