To set up a One-time schedule for a routine
Tap on the child to go to the 'Schedule' page
Tap on the '+' button
Select 'Just for today'
Choose the routine you want to create a schedule for. Remember you can only create a one-time schedule for a routine that you have already created.
Select the 'Start time' and 'End time'.
Don't forget to tap on 'Save'
Related questions:
Can I create a schedule for five minutes?
No, you can't create a schedule for five minutes. A minimum duration of 15 minutes is needed to create a schedule.