miter box for angled clip-on plinth

because when you cup this angled clip-on plinth with a normal miter box on a 45° angle th jonction is not correct,
two miter box, one for 90°wall angle and one for 45°wall angle.
I don't have print it yet,... when i will have time maybe, if someone make it and will test it, tell me if it is well functional, thx :)