ᐅ Single-family house with bay window on the ground floor and first floor – floor plan of the basement?

Hello everyone,

We are currently in the early planning stages of building our single-family home. I have tried out several floor plans so far and came across the following question.
If you build a bay window on the ground floor and first floor, how do you handle the basement (which is planned to be insulated for a separate apartment)?
Do you use the same floor plan as the ground floor, or do you try to keep the basement rectangular and build a slab foundation for the bay window on the ground floor?
Or is it an option to use the outer wall of the bay window and thus have a larger rectangular basement? In that case, I was wondering how the insulation of the basement ceiling would work if it no longer lies beneath the ground floor.

Thanks in advance!