There are many methods for making flying geese. If I want scrappy ones, I use the method you are using here. That allows me to use different triangles on the corners.
A very popular method makes 4 at a time. There are others as well. I'd suggest checking Pinterest and search "flying geese tutorial". Regardless of the method used, be sure you are cutting accurately - my biggest problem!
Also, as you sew them on, if you can't turn the iron on, you can finger press the first triangle back. That little step will get the corner all the way back and should help.