Chosen Solution

Would this work press hard on the back of the phone on a flat surface to pop it back in. If the iPhone has been thrown and the screen is popped out all over the screen

I highly advise you against that. So many things can be broken this way, internally, if the screen is pushed in an the wrong angle, or something like shattered glass is stuck underneath.

Is it the plastic frame of the screen that’s popped out or just the glass? If it’s the frame, I’d suggest you carefully open the screen and reseat it back properly. If it’s the glass, it’ll be more difficult. You could try heating up the glue w/ a heat gun to bond it back together.