Fresh from a trophy laden 18-month stint at Bayern Munich, Flick replaced long-serving Germany coach Joachim Low after Euro 2020.
Liechtenstein's goal lived a charmed life throughout on Friday (AEST), with it taking until the 41st minute for Timo Werner to break the deadlock.
The scoreline would have reflected Germany's dominance if not for Liechtenstein's goalkeeper Benjamin Buchel, yet Leroy Sane capped a fine individual display with a terrific strike to ensure there was no chance of a shock comeback.
Two of Flick's former Bayern players combined in the fourth minute, Sane teeing up Joshua Kimmich, who saw his on-target strike blocked.
Sane swiftly crafted another chance – Buchel making a fine stop to deny Werner – before Robin Gosens headed Kimmich's wonderful cross against the left-hand upright.
Germany's opener finally came with its 12th attempt of a one-sided contest, Werner slotting home from Jamal Musiala's flick after a brilliant run from the Bayern youngster.
Buchel somehow denied Germany a second before the hour, making a fantastic double save to keep out close-range efforts from both Gosens and Ilkay Gundogan.
Gosens finally seemed set to get his goal with a blistering strike that was destined for the top corner, yet Daniel Kaufmann's brave block summed up a stoic defensive effort from Liechtenstein.
Lichtenstein's resolve was finally punctured again in the 77th minute by Sane's brilliance, however, as the winger set himself up with some neat footwork before drilling a low finish across Buchel, emphatically making sure of the victory for the new boss.