Using guarded availability, you can block times for meeting directly your calendar and allow it to show up on your list of available times on your booking page.

Here is how to do it.

Step 1: Go on your calendar and block time off for a type of meeting with event title "#free meeting title" (see screenshot)

Step 2: Go to "Appointment Booking" on FreeBusy and click "Manage Appointment Types" on a booking page of your choice.

Step 3: Locate the Appointment Type where you wish to turn on Guarded Availability and click on "Change Hours"

Step 4: Click on "Advanced Availability Control" on your right and click on "Guarded Availability"

Now each time you are available for this type of meeting all you have to do it put #free events on your calendar and times will show available.