This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
洓 combines 氵 (water) with 朿, which is associated with thorns or piercing. The exact historical development is uncertain.
Water 氵 beside a thorny shape 朿 suggests something like water among thorns, but the meaning is uncertain.
For サク, imagine a sack floating in the water next to the thorny bush: sack -> サク.