Murphy's 45th law:

The secret to success is sincerity. Once you can fake it, you've got it made.

Mal als Ansatz ...

How about: self-confident appearance but totally clueless
i.e. " a phony"

Self-assertive presence in spite of complete cluelessness/ignorance.

Peter: I like your "Ansatz"!

@ Peter, you can fake it only once, after that you are busted. :-) :-)

Is' nett, nech? ;-)

Etwas enger am Ausgangstext:
Ignorance is bliss, the more so combined with self-confident appearance

Your Honor, I object!

If faking is successful, no busting is ever to be feared. ;-)

total self-confidence on top of complete ignorance

10 years after

Da der Faden schon mal da ist, re OP : Sicheres* Auftreten bei voelliger Ahnungslosigkeit

Wenn du schon den Woody machst, dann bitte auch: völliger.