VTT Map Hack for Impromptu Combat

I'm not the first person to come up with this idea (I checked via a thirty second google search) but I wanted to throw it out as a helpful way to run combat in a VTT on a grid.

Keep it simple by having a scene with a white background and a grid. You can do this in both Roll20 and Foundry, which I have used and I imagine you can in any other VTT. Then just draw the room or throw some squares or dots or circles if you have weird objects or difficult or elevated terrain bits. As in just do it rough like you would playing on a grid in person or back in the old days drawing on a piece of paper. 

Plenty of other people do unplanned encounters through theater of the mind, but I have players who get lost without the visual representation or enjoy the tactical positioning piece so I always play with a map. 

I think because of the VTT display and my own experiences I've always felt like I needed to have an illustrated battlemap. But you don't need to!