>>2965373It's not particularly difficult on the technical level. It just is very tedious when you have no muscle memory for photoshop.
>Find a background and foreground that thematically match in some way.>Render foreground.>Use LAB color adjustments to match light tones.>Add shadow and lighting.I find msinsanity's approach a bit overdesigned. The bloom and chromatic aberration is too much, but it could be achieved with some additional effect and blend layers.
For the first attempts it's often better to downscale the final result since it hides mistakes. Especially the render step is OCD triggering when you have to deal with holes in hair and stuff like that.