Ty,
I played around with stone windows using only slabs. I would create each stone mullion as a slab (rather taller than wide). group these. Then make another set that I would then create as a library part in order to rotate them horizontally. Then you can create yet another library part with the horizontal and vertical mullions together, and you are just about done. The glass and metal casement windows are more slabs along the same techniques.
If the attached image is what your are looking for and you need more direction, first look at the Help files under
"Doors and Windows", the part labeled
"Saving Custom Shape Doors and Windows from the Project File" , then let me know if you are still having issues.
Snap
PS From Lutyen's Marshcourt garden facade. I tried to create a stone texture that resembles the Cort used in this house.