spoon
匙 centers on a spoon: a utensil for scooping, stirring, or serving food.
匙 combines 是 (a phonetic component suggesting the sound) with 匕 (spoon), indicating a spoon. The exact historical development is uncertain, but the phono-semantic structure is broadly accepted.
The right side 匕 looks like a spoon with a handle and a bowl. The left side 是 can be thought of as a hand holding the spoon steady.
For シ, imagine a shiny spoon: the word 'sheen' cues シ, and the spoon gleams as you stir.