vase
罌 centers on a container for liquids or solids: a vase, jar, or pot. The single given meaning "vase" is the core idea.
罌 combines 缶 (jar, pot) with 賏, which likely contributes the sound. The character is a phono-semantic compound for a type of vase or jar.
The bottom component 缶 is a jar or pot. The top 賏 looks like a pair of eyes (目) above shells (貝), as if watching over the precious vase. Picture a decorated vase with a lid that has eye-like patterns.
For オウ, imagine an old vase that makes a deep "oh" sound when you tap it: oh -> オウ. The vase resonates with a long, low note.
common poppy (Papaver rhoeas); corn poppy; field poppy; red poppy