In most of my work I like to bring depth to a 2D composition. Either with light, depth of field or skewing and parallaxing.
Here is a scene I broke down to show how I proceed in order to give the illusion of 3D.
In this scene from John Kahrs Short film "JUNE" for LYFT, only the character is CG. The rest was created in Photoshop by the artist Arthur Chaumay.
I created a subtle push in and, by parenting the kitchen counter to the back wall, and applying the same scaling keys, It translated into a parallax that started to give the illusion of 3D.
Then I skewed the counter surface and counter-skewed the reflections of each object seating on it to make sure these reflections would stay straight while the counter's top changes perspective.
This scene is rather simple in appearance but it was one of the most complex I had to create on this project.