The area on the body to which each wing connects is 2x4 studs. The top row is filled with 4 cheese slopes, with the narrow end pointing upward. The bottom row has two hinge bricks with 2x2 hinge plates on top. These sit flush with the cheese slopes underneath, giving a stable angle that tilts the upper part of the wing inward. On top of the hinge plates is a 2x4 plate with 1x1 round plates added on opposite corners, with the rest of the surface of the 2x4 plate tiled over. You can attach another 2x4 plate to the 1x1 round plates at an angle, the distance is just right for that. I learned that latter technique from the official "Winter Toy Store" set, where it's used for the Christmas tree.