You should be able to figure out a good daily time for your team that doesn't involve breaking out of the middle of a flow state. Maybe when everyone is expected to be in the office, or even right after lunch?
The risk is always there. Say you schedule it at 8 in the morning? Then you might interrupt the people who come in earlier. Schedule it before or after lunch? Unfortunately people eat lunch at different times too. Schedule it at the end of the day? Then the daily standup loses it's effectiveness (while you risk interrupting people who flow later in the day).
There is never such a time, if you allow any kind of flexibility or self-direction in scheduling. Moreover, if you are customer-driven, you will wind up with having calls here, there, and everywhere, that some subset of your people will be on that clash with any potential standup time.