Abstract: A method of managing delivery resources comprising, for each of a plurality of delivery resources, defining a resource finalization time, an advance availability period, a deferred availability period, and a deferred availability release time. The method then further comprises, upon receiving a delivery slot request for an order, identifying delivery time slots for the order that can be fulfilled by one or more of the plurality of delivery resources, enabling selection of any one of identified delivery time slots, receiving a selection of one of the identified time slots and assigning the order to any of the plurality of delivery resources that can fulfil the selected delivery time slot and, after the resource finalization time of the assigned delivery resource, sending instructions to a storage and retrieval portion of the system to initiate picking and packing of the order, and loading of the order on to the delivery resource.