cloth
帛 centers on woven fabric, specifically a type of silk cloth. The meaning is straightforward: a piece of cloth.
帛 combines 白 (white) and 巾 (cloth), suggesting white silk cloth. The exact historical development is uncertain, but the component combination is consistent with the meaning.
White (白) cloth (巾) is silk fabric. Picture a bolt of pure white silk cloth.
For ハク, imagine a bolt of white silk cloth being hacked from a larger roll: hack -> ハク.