Hi to anonymous who has put in a request. I wrote up about chicken doorsteps last August and I only ever made the one. I think, if I was to do it again, I would do a 5 sided pyramid. That is a square at the bottom and attached to it 4 equilateral triangles. eg if the square is 12cm, then all the triangle sides have to be 12cm. That way you can get the beak and the crest in the "correct" place. Plus I used velcro as a trial on it, and I wouldn't use that again, either a zip or sew it up. Also for strength sew each side 2 or 3 times.
Hope that helps! Let me know how it goes!