I work in greyscale so I dont have to worry myself about having a background in every panel (this can also apply to my colored episodes. But when I do, I always draw them out. I dont think there are any 3d modeling programs for photoshop plus I feel that me drawing the backgrounds is more efficient than if I were to use one of those programs. For me, backgrounds can be quite fun to make in most cases. A lot of the time I wont use a full on grid layout, mainly because I'll already have some basic idea of what I want the perspective to be (and also because adding something like a horizon line can actually complicate things). That's not to say I wont use perspective lines for guidance though, but no horizon line in those cases.
For backgrounds, I'll usually reference google maps since my series takes place in an irl setting. But for certain locations, I'll use a set replica of said locations that I made in Minecraft right before I started working on my series. For example is one of the main character's houses which appears in episode 7. And the replica is far from being some hallow shell. It has an interior with multiple rooms and details such as couches and where paintings are. It really comes in handy when I was drawing the scene inside the house since I didn't have to worry about going off a vague image of what I wanted. No tracing involved btw. Would be impossible especially for the Minecraft replica sets.
I always try to go for a simple but detailed approach to backgrounds. There was a time where I my backgrounds were very basic and baron without any detail. This was the case when I was drawing pages traditionally, as I knew that any background Id try would be ruined when it came to inking (I hate inking traditionally). But with episode 5 and onwards, I switched approaches. I dont want to make my backgrounds so basic that their on the border of lifeless but I dont want to go overly detailed on them, mostly because I cant. Too much detail in a drawing is too much for my brain to handle and it can lead to whatever Im drawing or whatever Im looking at becoming unreadable because of how overwhelmed I get. I have to tie that fine line when drawing backgrounds weather it be a large city scape, crowds or train tracks, it has to be detailed enough to look good by simple enough to understand.