ladle
柶 centers on a ladle, a handled utensil for scooping liquids.
柶 combines 木 (wood) with 四, which likely contributes the sound. The character likely originally referred to a wooden ladle.
A wooden (木) ladle with four (四) scoops carved into the handle, making it easy to remember as a ladle.
For シ, imagine a ladle made of shiny (シ) wood: shiny -> シ, and the ladle gleams as it scoops.