Alright, so a move without mistakes would be:

- Select piece with one tap.
- Select destination square with one tap.
- Tap clock to confirm move.

This is quite familiar for chess players, that tap a physical clock in tournaments once they are done with their moves.

We need to have a UI making this evident for first time users, either with a very visible highlight of the timer when it's the time to confirm the move or with those instructions in the 3 first boots. Probably info in the banner is enough to start with.

What about games without timer? ."OK" button in the position of the clock? No games without clock to start with? I'm more for the latter.

Also maybe there are users that prefer to make moves without confirmation. This can be an option in the setting but, like many other possible options, I would leave it for later if there are real requests from users.