We currently do not have a waiting list feature, but some Full Slate users have used the following workaround to offer a wait list to clients.
1. Add a staff member under Setup > Staff with the name "Waiting List." (Don't worry, we won't charge you more for the extra "staff". Just email firstname.lastname@example.org to let us know how many actual staff you have, and we'll adjust your account accordingly.)
2. Add a service under Setup > Services such as "Join the Waiting List." Go to Setup > Staff and assign your "Waiting List" staff member to perform just that new service that you just added. You will be able to do this via the "Performs" drop-down. We recommend also adding a note in the "Overview" section for the service to let your customers know if they don't find the time they want, they can book an appointment by clicking on the "Join the Waiting List" service.
3. Under Messages > Automatic Messages you might consider applying overrides to your appointment reminders and confirmations and exclude the "Join the Waiting List" service. You could even add a custom appointment confirmation template just for your waiting list service to let them know that the request has been received and that you will reach out if the time they want is available. More on how to apply a custom message to a particular service: http://support.fullslate.com/hc/en-us/articles/201098618. This will make sure only your clients with actual appointments receive the appropriate communication.
4. If someone books into the "Waiting List" staff member, it will show up as an appointment on the Schedule tab. You will then want to reach out to them if their "requested" time becomes available.
If you have any questions, feel free to reach out to our support team at email@example.com.