> Voltage is made out of flow of positive electric charges.
Not really. What usually flows (in metals) are electrons. Quarks stay where they are. And when we prefer to think about flow of positive charges, the positive charge in question is a hole left by a missing electron. Physically real positive charges (ions) can flow in electrolytes though.
The concept of "flow" is questionable though. Bubbles in water move upwards, but it is actually water that is flowing downward around the bubbles. Just because bubbles do not contain water, we can't say bubbles are not flowing.
When it comes to electrons and positive charges, their material existence is equally non-physical. Actually, none of them might be "flowing", as the concept of flowing applies only to physical things that occupy some spatial volume and spatial location.