WooCommerce Bookings

I am creating a booking system for a workspace. people book in hourly slots. I want to have the provision to book slots on the hour or at half past: 12:00, 12:30, 1:00, 1:30 etc.

The only way I have been able to get the half hourly slots to appear is by setting the blocks to 30 mins but we do not allow bookings of 3.5 hours it must be 4 hours.

So what I am requesting is that someone could book for 4 hours at 1:30pm, thus getting the half hourly slots to appear without having the blocks set to 30 mins?