A direct, non-iterative procedure for the design of the magnetic element of the Flyback converter - the coupled inductor which is sometime referred to as the "flyback transformer".
Please see the background material at:
ElectroicBits#9 HF Transformer Design
https://youtu.be/3nfqBzPMknY
and
ElectronicBits#22 - HF Power Inductor Design
https://youtu.be/6Mi8QDD71vE