Preload Future States in Create?

[Mastastealth]

I'm a first time user of Phaser, been trying to make a simple point and click type game. I'm trying to keep things very modular, so I'm defining a list of levels (states) in a JSON, and then every level has its own JSON containing the objects within that level.

 

However, I'm encountering an issue in that, when changing states, I get a black flash while the assets for the next state load (this happens whether I iterate through the JSON list or define everything manually). From what I've read, all sprites should be loaded in the preload stage, however, by doing this I'm causing that tiny but noticeable black pause.

 

I know one way would be to simply load every asset at the start of the game, but that seems incredibly inefficient (wouldn't that fill up the memory immensely?). I would rather load a state's assets from the "parent" state. However, in my quick test (which maybe I did wrong) it seems that game.load doesn't work properly if done within the create stage? What is the best approach to doing this?