It takes 1-2 hours to setup a new laptop, email, other services with most of the laptop work automated using a MDM (Jamf in our case, although I would suggest looking at alternative vendors). Day of, it should take the new developer 1-2 hours to get fully set up with their dev environment since we use Docker Compose and keep the onboarding instructions pretty smooth. We used to have devs start working on a ticket after lunch, although now we're doing various training throughout the day.