salted meat
醢 centers on meat preserved with salt, specifically salted meat or a fermented meat paste. It is a rare, specialized kanji for an ancient food preparation method.
salted flesh (fish, etc.)
醢 combines 酉 (a jar or vessel for fermentation) with a right side that likely relates to meat or preparation. The exact historical development of the right component is uncertain, but the character as a whole represents salted or fermented meat stored in a jar.
The left side 酉 is a sake jar, suggesting fermentation. Picture a jar packed with meat and salt, left to ferment into a savory paste: that's 醢, salted meat.
For カイ, imagine a jar of salted meat so pungent it makes you cry out 'KAI!' as you open it. The sharp sound 'KAI' matches the reading and the strong preserved flavor.