First, cut off some wood timbers to 15.5*25.5*145mm. This is just my geometry. If you want more long grip, you need extension as you want.
The square,15.5*25.5 is much important number. So I cut a timber little big and after change it slowly with something like plane or files.
After all, cut some corners off if as the wooden core can be set in your silicone mold.
Make silicone mold of your master piece. It's better to coating your master with primer/surfacer because resin have construction factor.
Before casting, coat wooden core with something like varnish to prevent bubbling.
Set wooden core into the silicone mold and cast epoxy resin.
Now as you know I'm considering to order my new sticks. I bought a QRL stick from my local shop though, I can test it under very average environment. I'm feeling it was really good work for my hockey life.