I am no expert but, as a junior power electronics person I can say that:
The shunt capacitor depends on the ripple allowed but probably around 470uF or so will probably give a smooth output. The diodes and the power MOSFET should be fast switching.
But,
Designing forward, flyback or similar converters involves designing the transformer in the first place. I do not know if some exact values could be given without completing that phase first.
Considering a fine DC, you should find a suitable turns ratio then selecting an appropriate Lm value to enable a power transfer you should determine the number of turns.