How to stop ProBuilder from aligning new shapes with faces?

I feel like I've looked everywhere. Maybe I've missed it in settings somewhere, or it's a hotkey or something, but I can't just make a cube over a surface without it inheriting the rotation of the face directly behind it. I don't want this, I'd like to have the new objects align to the grid, and not just random geometry behind what I'm trying to make. Here's a picture:



As you can see, the blue cube is aligned with the slanted surface behind it, despite that not being my wish. I don't want this behavior in general, it makes working with ProBuilder in scenes with ground meshes that have even slightly slanted surfaces (aka pretty much every ground mesh I make) really unpleasant and slow. I'd have to make the shapes in open space, and at that point, I might as well just crack open Blender, rendering ProBuilder pretty much pointless. No amount of holding CTRL or turning on snapping, or changing pivots or anything is helping. Is there really no way to disable this functionality?