Flexibility is easy to promise and breaks in the details. These are ours.
Results, not presence
What gets assessed is delivered work. There is no credit for being online, and going offline is not a signal to interpret. If someone solves in four hours what was scoped at eight, the result is that they solved it — not that they have spare hours.
Asynchronous by default
A meeting is the most expensive way to communicate, because it blocks several people's time at once. Writing costs the writer more and everyone else less, and it leaves a trace. So writing is the default; a meeting has to be justified, not the other way round.
That carries an uncomfortable consequence worth accepting: if work is asynchronous, replies take time. A team that calls itself flexible while expecting immediate answers is not flexible — it is synchronous with longer hours.
Where the limit is
Flexibility cannot mean permanent availability. That you can work at any hour does not mean you should, and an organisation that fails to mark that line eventually erases it without saying so. The commitment includes the rest, not only the freedom.