Load scene in background and move into it without "loading"

When we typically load a scene, there is some delay during the transition period. That is, we might use a “loading” animation of some sort to show the player that the next scene/level is loading.

Imagine we have a door to a new room and that new room is its own scene. The screen might fade to black as we enter, there would be a delay and then the new scene would fade in.

I am looking to load a scene in the background and have it ready-to-go, so that the player can simply, using the door example, walk through into the new scene without any delays.

Does anyone know how I might achieve this?

You might want to use sorting layers? and activate the scene in a sorting layer script.