Everyone does things a little differently. You'll find several ways work to accomplish what you want, but there may be better ways. The strength of the forum is learning new ways people do things that we may not have thought of on our own.
I personally like to get my foundation model all on it's own drawing. Then, I place the framed walls, interiors, etc of a walk-out basement on it's own drawing. Where foundation walls are still present at the uphill side, I copy the walls from the foundation and paste in place, but turn off clean up and 3D extraction so the actual foundation is all that shows in the model. It gets into some duplication, but best allows for the model to be broken into pieces.
I don't recall any particular forum thread or training online, but probably picked up the tips on how I do it from some of the gurus on the forum. Some of them used to put on seminars before SP started doing their own training videos.