Tray

A recess cut into the plate that holds other parts: keys, a selector, an empty state waiting for its first thing.

The upper wall is in shadow and the lower lip catches the lamp: that is what makes it read as cut in.

• A tray is presentation. When its keys are one control — only one can be down — use a selector: it is a real radio group.
• An empty state says what goes here in words; the unlit lamp is a second signal.