What is the best way to: To cut the ceiling for a club house made out of cardboard.

Select from the following.
[A]. I use another cardboard to cut out the roof plate. If you don't have a wide enough piece of cardboard, then just glue several parts together.
[B]. I use another cardboard to cut out the roof plate. If you don't have a wide enough piece of cardboard, then just glue several parts of paper together.
Answer:
[A].