I don't think it's possible to just "think up" true AI. I think the easiest method to achieve it, would be to first upload an actual human brain to a computer

I don't think it's possible to just "think up" true AI. I think the easiest method to achieve it, would be to first upload an actual human brain to a computer environment - by slicing a brain into molecule-thin slices, then observing the neural responses of that simulated brain.