After work at the store that day, I took a detour.
After finishing work at the store that day, I took a detour.
After finishing working at the store that day, I took a detour.
Are the three grammatical/natural-sounding? Why or why not?
Here are my opinions:
After work at the store that day, I took a detour. Good.
After finishing work at the store that day, I took a detour. Good.
After finishing working at the store that day, I took a detour. Ehh... maybe.
The first two examples are clear and correct. I will point out that, in the second example, finishing is a gerund which takes an object, work. This is a common use of the gerund. In the third example, finishing is a gerund which takes a gerund as its object. I'm not sure whether this is good style. I would hesitate to write this in any serious document (essay, report, et cetera). But colloquially, you might hear people say this.
I actually like the second example best. The gerund in the second example somehow unifies the clause. The first example sounds a little choppy, although I don't see anything wrong with it.
The first two would be fine, whether or not the syntax is doctrinally correct in the first line. Nobody really expects you to have perfect diction in a conversation. The third one sort of makes it sounds like you quit your job and then took a detour though.
I think it sounds janky because you took a detour from what? Why not "My work being finished for the day, I soon found myself sidelined as I encountered a detour on my drive home." Just saying "I took a detour" invites cognitive dissonance...you were just talking about work, so do you mean you took a detour from your normal routine by entertaining some new pursuit, or that you were literally rerouted by road signage through a detour on your drive home? The economy of perception working within the reader is conflicted as to your meaning. Taken out of context, this is jarring, yet intriguing. If you are trying to create this confusion to lead into something that will resolve it, then perhaps that is the way to go. If you leave this dissonance unresolved, the reader is left feeling like you made a promise you didn't keep, so they will pay less and less attention to subtle meanings in your sentences, until they lose interest entirely. Was this a grammar or a writing question?