What attaches the "I" to a body or to some set of cells? Is the attachment done at the cellular level? At the neural network level? At the systems / input-output level?
The consciousness is no more attached to the brain than say the colour blue is attached to the sky. Just like the perceived colour of the sky, consciousness is an emergent property of the interactions of the neurons and synaptic connections. It isn’t a ”thing’ in it’s own right, but the sum of all the activity in the brain.
You can take a symphony apart note by note and examine each in turn but you won’t find the tune, the harmony, the emotion. Same as you can’t take a brain apart bit by it and hope to leave the mind. It don’t work like that the mind and consciousness, like a melody, are the sum of the total interactions in the brain and the nervous system.
Neither mind nor melody has existence outside its regimented structure of notes or neurons but we perceive them both as an almost tangible things despite their illusionary nature.