You can use peak hours to add additional time to the Default Preparation Time, you can also throttle orders based on Amount or Order Count which is explained below.
Control Panel > Configuration > Peak hours > Add Peak Hours
Select the Start Time for the Peak Hour.
Select the End Time for the Peak Hour
Enter additional Delivery Time for the Peak Hour.
Enter additional Preparation Time for the Peak Hour.
Mark the days the Peak Hours are valid for.
Enter Order throttling Count, so if you enter 10 here then during this peak hour the system will only accept 10 orders in Total .
Enter Order throttling Amount, so if you enter $1000 here then during this peak hour the system will only accept $1000 worth of orders in Total .