I realize there are 2 ways to illustrate a script with stock footage.
One way is to simply use footage that matches what the script is about, for example for a script that talks about being rich, the footage would show a man with many banknotes and a luxury car. That would turn into a boring illustration because it shows what we already know.
The other way is to use footage that correspond to a thought with an extra step and... this is the a concept I don't fully understand so I would like you to explain it, with many examples.