Start by cutting the video track.
Solder the wires to the receiver board. All the solder points are good sized and easy to solder to.
Now it is time to prepare for soldering the wires to the the minimOSD board and mounting it with sticky tape. All the solder points on the minimOSD are through hole, so the soldering is easy.
This is the finished pcb layer cake from the side.
The only thing left to do is to turn the boards over and solder in the buzzer. A few dabs of hot glue does a good job of holding it to the edge of the receiver PCB.
This is the finished pcb layer cake from the top. It will slip into the original holder without any modifications to the rest of the googles.