Modular geometry not snapping properly once rotated

I’ve been working on modelling modular pieces for a new project, however I’ve run into a problem:
I’ve just made a corner piece which aligns perfectly with the first few pieces, but once I try adding another rotate piece the grid snapping in the Editor no longer manages to snap them in place properly.

I feel I’ve not explained this super well, so allow me to call upon two images to help illustrate my problem better:

Is there any way to fix this in Unity without needing to almost completely rebuild my models?

Fixed it myself:

I was rotating the objects around their centers, and not their pivot points that I had set in Blender.

Rotating them around the latter has them snap to the grid perfectly.

(Each model takes up the entire 16x16 grid space in Blender, and their origins are set to the center of said grid)