open space, field, market
塲 centers on a flat, open area used for gathering or activity: an open space, a field, or a market where people come together.
塲 is an older variant of 場. It combines 土 (earth, ground) with a phonetic component that historically contributed the sound and the idea of an open space. The modern standard form 場 replaces the right side with 昜.
The left side 土 (earth) suggests a flat piece of ground. The right side looks like a sun 日 over a shape 勿 that resembles a market stall. Picture a sunny open field where a market is set up on the earth.
For ジョウ, imagine a large open field where a show is being set up: show -> ジョウ, and the earth 土 is the stage for the market.