Here is how I do the other tree. First I cut several triangles ranging in size because trees are smaller at the top.Then I sew a little strip of white to each side of the triangles and fold and press it back. The angle that you sew is up to you. I have tried a couple of different angles and you can see which you like better at the end of the post.
Turn the triangle over and trim the white off to match the green triangle.
Oops, there is a bit of green showing on the corner but I won't worry about it because it will disappear into the seam.
Add the blue background the same as for the other tree but put it on both sides of the triangle. This time, I sew the triangles all the way across, tipping them at an angle to make it look more interesting. Sew a strip of white on the bottom for snow. You could put a trunk on but I don't think you normally see the trunk on this kind of tree.
Here are two finished ones with the white sewn on at different angles. I prefer the one on the left and the top triangle is my favorite. I like the way it is more snowy on one side. It would probably look good if they were all done like that, or it might look lopsided. You can't tell until you make them. That's why I often end up with a forest when I was planning to make only one tree.