Hey Danvers! You can accomplish this workflow in 2 Zaps, using the built-in Formatter, Digest, Filter, and Schedule apps. Here is how you'll want to lay them out:
Zap 1
The purpose of this Zap is to grab all of the events in the next 23 hours and add them to a digest at 7am tomorrow morning.
Trigger: Event Start Google Calendar - 23 hours before the event
Action: Formatter (Date/Time) to format the date of the event into a readable time (optional)
Action: Digest - Append Entry and Schedule Data.
Zap 2
The purpose of this Zap is to pull the events out of digest and post this list to Slack.
Trigger: Schedule (Run Every Day at 8 am)
Action: Digest - Find Digest (the one created in Zap 1)
Action: Filter - check to see if there are events in the digest
Action: Digest - Release Existing Digest (the one Found in step 2)
Action: Slack - send direct message with the output of the Digest
@iDog I haven't seen the Outlook Slack app before, that's pretty cool. I don't use Outlook myself, but I like the feature of being able to RSVP to a meeting directly in Slack :)