I'm trying to figure out how drywall is supposed to be cut out to go around preexisting electrical boxes that are attached with rigid metal conduit. The conduit is the ground path. My dilemma is if I disconnect the box from the conduit and then push the box through the front of the drywall I won't be able to access the back to reattach the conduit. If I put the drywall over the box I'm not sure how to get the "ears" through unless I make the cutout large enough, but then the ears won't have any material to since against.
I've attached an image that shows the box as well as how a box on a different wall that is already installed looks. The ears on the box are detachable, but I don't see how I could even access the screws to secure them after the drywall is placed over the box if I remove the ears first. The already installed box isn't shedding much light on how they did this, so any advice would be appreciated!