Find the slot that works across six calendars

Scheduling across more than three people is not a hard problem, it is a slow one. Everyone can see their own calendar and nobody can see the intersection, so the work becomes a thread where six people each report their availability badly.

Connect the calendars you can actually see

From Integrations, connect Google Calendar. You will only ever get the intersection of calendars you have access to, which in practice means your colleagues rather than the customer.

That limit is worth stating out loud, because it decides the shape of the answer: for internal meetings you get a slot, for external ones you get two or three good options to offer.

Ask in one sentence

Find me 45 minutes next week that works for Ava, Marcus and Priya as well
as me.

Working hours are 9am to 5pm Denver time. Do not put it inside anyone's
existing meeting, and do not book the half hour either side of one.

Give me three options, best first, and say who is tight on each one.

That is the whole thing. There is no setup, no availability poll and no thread.

"Say who is tight on each one" is the part people leave out. A slot where three people are free and the fourth has ten minutes either side is not the same as one where everyone has room, and the difference decides which option you actually pick. An intersection with no context is a worse answer than it looks.

For external meetings, ask for offers rather than a booking

You cannot see the customer's calendar, so anything that claims to have found a mutual slot is guessing.

Give me three 45 minute options across Tuesday to Thursday that work for me
and Marcus, written as a sentence I can paste into an email to a customer.
Use their timezone, which is London.

The timezone instruction matters more than it sounds. Offering times in your own timezone to someone five hours away is the most common way a scheduling email costs an extra round trip.

Let it book once you trust it

For internal meetings, the follow-up is simply "book the first one and invite them". It creates the event and sends the invitations.

Do that by hand a few times before you let a scheduled job do it unattended. Booking is a write on other people's calendars, and it is worth knowing what it does before it does it while you are asleep.

What good looks like

The question "when can we all meet" stops being a thread and becomes a sentence.

The failure to watch for is a slot that is technically free and practically useless: back to back with something else, or in the half hour someone always does the school run. Calendars do not know about the second kind, so if a person keeps rejecting good-looking slots, add their constraint to the prompt rather than assuming the tool is wrong.