Is there a flag for flagging as insufficient research effort? Or do I need to use a custom reason flag? (Should I even flag a question as such? I know a lot of people do...)
Sorry if this is a dumb question.
At this time, there is not a flag for insufficient research effort. And I would say you shouldn't flag for that. If you have the ability to vote to close with a custom reason, you can do that, and downvoting is also a good idea, but it's not the sort of thing we're really comfortable handling with unilateral moderator action.
We have been talking about replacing the homework policy with a new policy which will likely focus on insufficient effort. So when that process is complete, we probably will have a close reason (and a flag) for it.