Cut off the red lines of part(1), and fold it half.

Paste part(2) and part(3).

This is a tree.

Fold and paste part(4) as this illustration.

Paste part(5) and part(6). Then paste part(4) to it.

Fold half and paste part(7).

Paste part(4) to inside part(7).

Paste each parts to the base.
At last, paste cover paper.