appointment+ time frames. Would like to have open time slots

Need some help, Im using this plug in to take Appointment for Recording Studio Booking. Currently the calender is set up in blocks, meaning if i open at 8am and close 11pm and studio sessions start at two blocks, customer have to select a 8am-10am,10am-12pm,12pm-2pm ect... I would like it set up to were a customer can decide to come at any time of the day, say maybe 9am and set a two hour block from 9am-11am, and then say someone wants to come at 1pm-3pm. So they are not obligated to select the 8am, 10am or 12pm start time. They can start at anytime.