For me background is part of the whole scene. I do not make characters outside of the environment while I can do environments without characters. If that makes any sense.
I have two approaches. Background is either a character or is the main focus of the image. I still struggle with dynamics and movement, but otherwise I find it fun process to build environments.
There are two things you might struggle with - separately and you ought to practice them ... separately.
Issue one : you can imagine, but cannot draw
Issue two: You lack the experience to imagine (inability to see full scene outside character)
You can practice the 'scene' building by using your phone camera and photographing objects around you and then analyzing the images. You learn quickly to see that person/object never exists in vacuum. In photography and in film the important elements are composition and framing. When you photograph random objects - try to have good composition and nice framing. Eventually you build up experience and eye to SEE the environment around your characters or objects.
I.e. simple background. Character drinks coffee - where ? When ? morning, kitchen. There, you can just have simple counter and maybe window that shows outside. Simple!
A teen character ? So they scrolling phone? somewhere in school, somewhere in public transport? Easy!
Before you can draw a background and practice drawing background, you ought to learn to see objects in environment and photography helps you learning this.