How to disassemble these parts?
I don't know what pieces you have in your collection to build the perfect most creative piece separator, so my answer will be based on, "What common items do many people have on hand in a house?"


Try a dull butter knife.


EDIT:

Or we can just ignore what I said, and make something simple with pieces many of us should have.


Find any sized beam 5 pin holes or above.
Insert some pegs in the holes.
Place stuck pieces on top.
Apply downward pressure mainly holding from the black piece (Part 32017) to create a starting point of separation.
Once a gap has started it can be easily "unzipped" apart by running a
finger nail/plastic knife down the gap.