small dish, plate
碟 centers on a small flat vessel for serving or holding food: a small dish or plate.
碟 combines 石 (stone) with 枼, which likely contributes the sound. The stone radical suggests a stoneware dish or plate.
The left side is stone 石, and the right side 枼 looks like a flat, segmented tray. Picture a small stone dish or plate made from a flat stone slab.
For カツ, imagine a small stone dish holding a crispy cutlet (カツ): the cutlet on the plate cues カツ.