Drywall around 10x10 electrical box
You need a flush mount cover for that box

What your electrician did was install a standard NEMA 1 (indoor) enclosure/pull box there, and these by and large come by default set up to be surface mounted with their back to a wall, for use in industrial applications and utility spaces.  However, for a finished application, you need to fit a flush mount cover of the correct size to the box instead of the stock surface mounted cover.  It looks like you'll also have to unmount and remount the box, with the breaker for that circuit or circuits off, so that it is actually flush with the finished surface, instead of being recessed slightly, as the flush cover won't fit properly otherwise.