There are many theories of consciousness but nobody knows if one of them is correct and nobody can use one of them to build a conscious machine. Compare that to theories of physics. None of them is 100% correct but they give us the tools we are using to write these messages.

I've got a theory of consciousness, not a very complicated one, that could be used in a machine. Basically that it evolved as a practical way for animals to make decisions like whether to run from a predator. To do that info from the billions of neurons handling senses memories and the like filter down to something like a situation summary, which is basically what the animal is conscious of which then feeds to the decision making, thinking and remembering and neurons.

It would be quite interesting if/when someone tries that to see how close it is or isn't to nature.