Hello David.

Thank you for your purchase.

When you have multiple locations, you need to assign a specific employee to that location (through Employee settings), then have that employee assigned only to services that are being handled on that location. This way, one employee will be assigned to services which will be used on that location, while other employee will be assigned to services used on a different location.

If you meant to ask to choose a custom location by the user in front-end, unfortunately that cannot be done. The only thing you could do is assign a custom field (in customize settings), where they would enter the address where service will take place. But in this case, you don't need to have any locations created.

As for the duration - you can only set the timeslot to a lesser value, and once the service has been scheduled, based on your experience on how long it usually takes, you can add a couple more timeslots, so they won't be booked by someone else.

Best regards.