Shipments would normally be processed in the 'front office'
where orders are entered. The label (and packing list) would then be clipped
together and passed over to the warehouse for picking.
Now that pick and pack has been configured, the shipping screen has the scale later option:

This can be used on some or all shipments. Labels will print as usual. (Ignore any weight or rate information that appears when the shipment is processed.)
Using Scale Later is a perfect time to use AutoShip
templates to speed printing of labels.
The key is that shipments processed this way will not upload until package weights have been set.
Next: Settings Weights and Dimensions Interactively