I clicked on the flag button in a game to resign, but my clock continued ticking.

Do I have to do something else to resign?

double-click it.

Double click resign is a clear design error. Buttons should only need to be clicked once, like real buttons.

In the case of resign I disagree. In case of a bad click it is good to require additional action for confirmation.

Click your name, go to preferences: Scroll down to "Confirm resignation and draw offers", select No.

Yeah I agree, I've always wanted to be able to accidentally resign a game

Yeah or my kid to reach over and do it since he wants my attention, which he has tried

Well, didn't say it was a good idea, but it can be done :)

It's just for confirmation. You can change it in the settings.

@ProfessorBooty
For confirmation, a confirmation dialog box is the appropriate solution. A two time click button is going to be misunderstood by a lot of people.