Honestly, all methods I read above (I may have missed this) are more complicated than they need to be. The easiest way in my opinion is to just use a potentiometer as it never loses the angle value even when off. The only downside to these are they have a max of approximately 270 degrees of rotation. We use potentiometers for claw and lift tracking to allow us to do auton. It checks the current position and depending on that, spins the motors till the desired angle is reached.
So when we are building, we need to make sure the position we keep it in is correct