If I have one house brick next to another house brick and next to another house brick and I add 10 house bricks to each, they are all the same height (pre-flashing). However, if I put three house bricks one on top of one and 10 house bricks on top of the next and 30 house bricks one on top of the next and I then add 10 house bricks to each I have a variance of height (post flashing). Do you get my drift?
Isn't pre-flashing sort of like pre-visualisation?
In a flood zone, I'd rather put them on the bottom. If I wanted a rooftop viewing deck I'd put them on top.
Your second example sounds more like first burning, then flashing.
At least with LF landscape, a bad day of photography can be a good day of exercise.