Prepare the pattern for the FOREX frame.
Fasten a large sheet of paper on the frame of the skylight with magnets.
Now you can easily mark the outline of the skylight and the positioning of the screws on the paper.
Transfer the contours of the skylight and the positions of the screws onto the FOREX board.
Fasten the paper on the board with adhesive tape strips to keep it in place.
You can use the carbon paper for that or just make marks with a pointy object through the paper onto the FOREX board and then connect them on the board with a pencil.
Cut the frame from the board with a box cutter and drill holes with 10 mm diameter for the magnets.
Put adhesive tape on one side of the FOREX frame to close the holes on one side.
Insert magnets and apply adhesive tape on the other side of the frame.
The magnets are now flush embedded in the FOREX frame and can no longer fall out.