AOB9;
My (former) airline (I'm now retired), extends flaps to the takeoff position, (as planned and calculated during the cockpit check), after engine start and before taxi as part of the After Start Check.
The only time that procedure might not followed is in winter where the aircraft is to be de-iced first because it is snowing sufficiently so as to contaminate the inner leading edge surfaces (behind the slats) as well as the surfaces of the slotted flaps. The "After Start" check is then completed. The slats/flaps selection is left to just prior to takeoff if there is either freezing precip or wet snow falling - same reasons.
In the light of some comments on the thread, some may wonder about this procedure but in such weather, one is caught either way by risks which must be managed: - contaminated surfaces and/or a checklist item, either of which, if not respected, can produce the same outcome... The SOP is to extend slats/flaps just prior to takeoff in the above conditions, (which of course present their own separate risks and requirements).
However, the Airbus has a robust TOCW system which is tested as part of the Before Takeoff checklist and which will sound an aural warning plus light the Master Warning (red, for non-pilots) in front of both crew members when the thrust levers are placed in the FLEX/MCT or TOGA position. The TOCW is cannot be disabled by pulling circuit breakers.
I have done a max-pitch takeoff in the sim, (sidestick full back to the stop) where the alpha-prot mode maintains a "suitable" AOA (pitch around 25deg) while enabling 20deg-bank turns...once again, with slats/flaps in the takeoff position, (1+f). To be clear, I am unsure how this aircraft would perform in any slats-up/flaps-up takeoff but I'll bet some are trying it out in the sim as we write.