Tools:
Drill
Sandpaper
Saws (Pull stroke thin ones, big old cutting log ones)
Wood ( What kind? ) ???
I was thinking of using Duncan guts, and use the drill to bore a hole through a roughly circular bit of wood, put it on a drill, sandpaper to some basic rounded butterfly shape, and use the duncan guts to hold an A sized bearing. And drill out a flow groove response too… is it possible?
Even turning a yoyo on a lathe is a very hard, but rewarding experience. I made a few on a drill press. They were horribly vibey but nonetheless it was cool because I made it.
Then again i am awful at shop stuff, so you might have better luck than me.