It is built into Google calendar. But the gcal version has horrendous UX.

It’s called appointment schedule/slots.

https://support.google.com/calendar/answer/11608416

I love calendly because: 1) it checks my calendar for conflicts with a link or suggest times in gmail 2) adds zoom meeting details automatically 3) avoids having to do timezone math

I just send my calendly link and don’t have to discuss back and forth about who’s available when savings tonnes of time.