Hi there and welcome!
There is a dedicated thread on the OWA here on AFF:
"oneworld" award (132.4K/249.6K/318K/455K) Planning - The Definitive Thread
However, even for seasoned professionals, it’s really really hard to put something like that together. Availability is the key issue. It will usually take hours and hours of planning, before you can even start to book. And even when you can book, you’re unlikely to be able to get all the segments you need form the outset, so you’ll need to call the call centre.
This in itself has a range of very significant problems.
My last OWA was easy, only because qantas released a whole bunch of award space as a ‘we’re sorry’ offering… and my award was really simple… QF to London, QF home from the states… so I just needed one transatlantic to find, which was on BA.
Trying to piece together an award when there hasn’t been a huge release of seats can be hard. The starting point is to lock in the long hauls. Look via Sin, Hong Kong, Tokyo etc. Worry about the european connecting flights later.
You might also want to consider a paid service where they find the seats for you. But that can be expensive.