How to build synchronous boost converter with IR2104 mosfet driver?
Does anyone know how to build a synchronous boost converter with
  IR2104 mosfet driver?


and...


  Any help would be much appreciated.


It's going to look something like this: -



Q2 charges the inductor from the main power rail by shorting it to ground and, when Q2 releases, Q1's diode will push the stored inductor energy into the load capacitor rapidly followed by Q1 turning on properly to act synchronously.

Be careful with this - if you have Q2 active for too long, the inductor might saturate and, on some supplies you might get Q2 burning.