You can manually add a booking within the CMS to block out dates from being booked.
Click the BOOKING menu on the left hand side and choose Add Booking, or edit a booking product and choose Add Booking from the small tabs top right.
As part of the booking you do not need to assign the booking to a customer.

Booking out time slots is handled by manually adding a reocurring booking to the required calendar
If you don't want to take bookings over a certain period, you can set a calendar resources Available From: date.
To resolve this issue when using the accommodation booking option, remove any opening hours set on the website.
You can manually add a booking within the CMS to block out dates from being booked