I saw one of them this Christmas in the house of a friend, made by their child in the school, and I fell in love, because it is simplicity itself.
I published it here because I could not find it published before, and I want it to be accesible.
Step 1: Needing... Near to Nothing.
You may want to draw a template.
Step 2: Hard to Explain, Easy to Make!
Draw a vertical line as shown (it will separate the wings), and the two (both left or both right) half segments of the horizontal one that will be the miter joint.
Cut by both circles, and the three lines, but retain uncut a little of the bottom of the inner circle, because it is the neck of the angel.
Twist the wings and insert each half of the miter joint in the other one, like an X, joining labeled points "a" with "a", and "b" with "b".
I can't explain it better, but it is very easy.