The organization has the option of including a section called Select shifts on a form.
This allows volunteers to include shifts as part of their submitted form. However, the volunteer still must get approved for the opportunity before the reservations are confirmed.
To get a better idea of how this works, it is important to understand that volunteers must be approved for an opportunity before they can officially reserve spots to shifts.

For example, imagine there is a volunteer named Sabrina. She wants to register for an opportunity titled Server posted by her local food bank. When filling out the registration form, she sees there is an available shift next Tuesday at 1:00 PM which she includes on her submitted form! However, before she can officially reserve her spot to the shift, the food bank needs to ensure that Sabrina is eligible to participate for this opportunit. Therefore, only once the organization approves Sabrina's registration for the Server opportunity, her reservation to the shift next Tuesday at 1:00 PM will be confirmed!