Should I flag an answer that is incorrect (in the hope that it will get deleted)?
For example, a post that has tried to answer the question, but the poster is clearly wrong and giving bad, or technically inaccurate, advice.
No, is the short answer.
It should not be flagged. It should be downvoted and a comment left explaining why it is incorrect.
This clearly leads to the question:
Why don't we delete bad answers?
There is a reason why the standard flag rejection message exists:
declined - flags should not be used to indicate technical inaccuracies, or an altogether wrong answer
And what is that reason, I hear you ask...
Well, there's a school of thought that says if one person thinking of something - be that an answer, question, idea, belief or assumption - then odds on, there is at least one other person thinking the exact same thing - be is a correct or incorrect assumption...
So, if someone posts an answer that regurgitates a mis-understanding, commonly held belief, an internet myth, or what have you, that has been proven to be wrong, then that answer should most certainly not be deleted, but held up as an example of inaccuracy - not to vilify the poster, but rather to re-educate, and hopefully try to stop the self-perpetuating inaccurate fact/myth in its tracks. To do that a down-vote, in conjunction with a comment, can help to do that.
Note that a downvote alone, without at least one comment, will not - as the poster probably won't understand why they are getting downvoted and just assume that it's some sort of vendetta.
There is some confusion with Not an answer (NAA) and Low quality answer (LQA), of which a technically inaccurate answer (as described above) is neither.
This is how a I personally interpret the flags:
This post by Shog is most useful and provides a pictorial explanation, Your answer is in another castle: when is an answer not an answer?:
My reasoning above is derived from a mixture of feedback that I have had from declined flags that I have raised over the years on Arduino, Raspberry Pi and Electrical Engineering.