My boss sits in a glass office across from my desk. Every morning he walks into his office, sits down and undoes his trousers. It took me weeks to pluck-up the courage to say something, but eventually I told him I didn’t think it was appropriate. He was shocked that I knew about it. Turns-out he thought that his office had one-way glass and didn’t realize everyone could see in.

What does “undoes his trousers” mean?
Well let’s hope it doesn’t mean what you are imagining Will. Undoing the trousers to let his gut fall out is bad enough.
What, he didn’t notice he can see into the office from the outside?