The tree is complete.
I alternated layers of gingerbread and sugar biscuits with sprinkles baked in. The gingerbread recipe was a nightmare to work with, very sticky even after chilling. It made a firmer biscuit than the sugar biscuits though.
Last time I made one of these I used too much icing between the layers and the biscuits could not be separated. I just did a few dots between each this time which will hopefully be enough to keep it together but still let it be pulled apart.