Can you let customers select their own start and end times?

I'm trying to use the Appointments plugin to take bookings for a room. Availability can be set fine, but customers can only book in set slots, ie. 30mins at a time.

The room is available for as long as customers want. Some may only want an hour, but others could book out 2 or more.

Is there a way that customers can choose their own start and end times?

Many thanks for your help