The fist method goes like:

1. Setting the flyback voltage: VOR

2. Calculation for the inductance of secondary winding: Ls, and the secondary side peak current: Ispk

3. Calculation for the inductance of primary winding: Lp, and the secondary side peak current: Ippk

4. Fixing the core size of transformer

5. Calculation for turns of the primary winding: Np

6. Calculation for turns of the secondary winding: Ns

7. Calculation for turns of the VCC winding: Nd

NB: Found this in a power supply design using BM1P061FJ document by ROHM Semiconductor.

The second method depicted in link below..

How to Design High Frequency SMPS Ferrite Core Transformer by Haseeb Electronics

I did not understand exactly the first one especially this VOR!! and the second one gets little bit confusing in the transformer core selection !!

Can you please say which method is best? and if there is a better method with clear instructions on how to design a flyback smps!