Step 2: Getting the work done
The drilling of holes on the cover definitely void your warranty!
Grab some sand paper and roughen the surface of the battery cover, this helps with the adhesion.
Spread the epoxy like butter, I use JB cold weld epoxy, it is supposed to be good, cures in 24 hours, I think super glue might work but it wouldn't be as durable. Also note that you have to attached the solar panel in the correct orientation.
Now as you can see, the holes let the epoxy escape allowing better adhesion, acting as 'grips'
That done let's wrecked the phone! :D
The only place that needs 'trimming' is a gap on the phone's naked frame, this allows a snug fit of the diode.