While installing a new piece of drywall into a painted wall with existing drywall of the same thickness, parts of the new drywall seem to sit or sink back further into the wall even with pressure evenly distributed on the new piece. I imagine this since the new piece is not pressed up against a stud.
What is the best way to resolve this gap?
At the base, the drywall pieces do not have this problem since they are both against a board.
What is the best way to approach in this scenario to end up with a smooth wall, is there some method to shim behind the drywall to get a more flush fit? Or does it make more sense to just install as is and apply joint compound until level?