you can print and tell the printer make the top and botton anyway wou want, lines in any angle or concentric.
my print is the worst quality I can get for a .4mm nozzle, its 0.3 mm layer height.
print quality can be increased a lot with a 0.1mm layer and a 0,3mm nozzle, of course a 0.2 will be better, I have a 0.3 to try, but I think the best way to do is simple, then sand, and spray with any paint.
will be nearly perfect...
the other option is print it in abs and acetone to do the soft edges, with a lot of caution, cause is a toxic quimic.
but I think paint it will be the best option to get a professional work.
then you can print a case cover so you protect the phone... I draw one some time ago, is posted somewere here