I would refine the instructions a little:-
Yes, put the 14 x 12 box on top of the National brood box (no queen excluder) and feed to encourage the bees to draw out the foundation. You do need a decent colony and not do it too early in the year or they will struggle. Put some insulation over/around the feeder. This DOES make a difference to uptake as otherwise it will cool down overnight and won't be taken down so quickly.
Once they have started drawing comb, put the queen on her brood frame in the top box and continue to feed for, say, another week; her presence will encourage the bees to do more upstairs. Then move the National frame down below the excluder leaving the queen upstairs. It might take a few days for the bees to get the message that we want the queen to lay in the 14 x 12's but after a week or so there should be eggs and small larvae in the 14 x 12 frames.
Now is the time to use a small eke between the two boxes...
Check there are no queencells in the lower box (unlikely but you do need to check). Seal up the hive entrance. Place a queen excluder on top of the National brood box, then a small eke (say 25 mm high) with an entrance. The the 14 x 12 brood box goes on top with the queen in, of course. The colony will re-orientate to the new entrance and will concentrate their efforts in the 14 x 12 box. Continue to feed gently unless there is good income. With the National brood box down below, bees will move stores up (they like stores above their heads) and by the time the brood has emerged from the bottom box (21 days from the last laid egg, or 24 if there is drone brood) there should be almost no stores in the bottom brood box which can be removed entirely; the entrance opened and the hive put back to 'normal'
I have tried to force the colony to work upstairs straight away by putting the queen on foundation only above the excluder. However you will probably see that after a few days the queen is just wandering around on the queen excluder and not doing much - and she could be ignored and get cold. The process has worked but is a bit harsh on the colony and I wouldn't recommend it.
May your bees read the same books as you do.