From Munawirrahman: Improve the Granularity of Your Flow Scheduling
Munawhir has created an installable Flow Action that allows the scheduling of Flows using the highly tunable Apex Scheduler. Previously available only to developers, this scheduler allows the creation of schedules that can be tuned down to the second. Here are some examples:
Note that an org can only have 100 of these scheduled events at a single time. Also note this warning: Use extreme care if you’re planning to schedule a class from a trigger. You must be able to guarantee that the trigger won’t add more scheduled classes than the limit. In particular, consider API bulk updates, import wizards, mass record changes through the user interface, and all cases where more than one record can be updated at a time. Using this with Flow, you can definitely schedule events from a trigger! More detail on scheduling is available here.