A full circle is 360°
With 8 pies sections (trees), each needs to be 45° degrees.
Therefore, IF each tree is 45°, they will go together to make a full circle.
Looking at the photo, each tree was made, then the trunk and white at the bottom was added.
Then a strip of white on one side, then the other side.
And back and forth til each piece of pie is to size.
The more white that's added, the bigger the circle will become.
Join the pieces of the pie together, leaving one open for your skirt opening.
If it were me, and it were for a novelty tree, I'd sew the eighth section from the outside in to the centre and leave just enough opening to feed the bottom of the tree thru. Would give a much neater and tidier look for oohing and aahing!
