This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. The modern form combines 木 (tree/wood) with 薄, but the original role of 薄 in this character is unclear.
The left side is 木 (tree/wood), and the right side is 薄 (thin/dilute). Picture a thin wooden pillar or beam, but remember the meaning is uncertain.
For ハク, imagine a thin wooden pillar being hacked into shape: hack -> ハク, and the wood 木 is being worked.