I would understand the key questions to be ones that you'd ask the children so that they understood what the activity was about and its desired outcome was achieved ... that you/they made a Christingle !!
If you look at what basic steps (method) you take to make the Christingle and then look at what sort of questions you could ask about each of them so that the children can understand what the activity is about and why they are doing it.
What the items are, their names and in this case their meaning.
What they already know about Christingles and where/what they associate them with.
Be careful of the amount of questions you ask though .. or the activity could take a week to finish
lol
Hope that helps, although you could always ask to see someone elses sheet and then compare the two
Let us know how it goes