1. A method of fulfilling orders, comprising: establishing a queue of orders that are available to be filled, each order in the queue containing at least one unique item type; selecting an order from the order queue and opening that order as a first order; selecting another order from the order queue and opening that order as a second order; delivering inventory containers each having at least one unique item type for at least one of the orders to an operator inventory container location and an operator picking the unique item type from the inventory container to assemble that order; assembling the orders at order assembly locations that are at different distances from the operator inventory container location; and assigning the assembly locations to the orders in a manner that improves order fulfillment productivity.