Hiromi explained it will be very tight to do with a 棚, and even if it were possible, it would be a pretty silly idea, since you want to spotlight the 香合 and not have any distractions.
You enter with 炭斗 and はいき, start 点前 as always. Then, when the time comes to lay the incense, you go out with the はいき, and come back with the 香合.
Once you've laid the incense (with your bare hands), you put out the 盆, then leave and return with the water jug. During this, the guest fetches the 盆, and commences 拝見 when you wet the 釜.
Guest asks for the ごゆいしょ; they turn it on the ground.