Every fingering that fits a hand
1312
moderate · barre
x878
easy · no 5
What is true of it
A♭m6 is A♭, C♭, E♭ and F — 1, b3, 5 and 6 counted from A♭.
These are also the notes of Fm7♭5/A♭. Which name is right depends on what is underneath and what came before — the notes alone do not decide.
On an instrument that cannot reach all 4, the 5 goes first, in that order.
The easiest of the 2 fingerings below is 1312: 3 fingers, one of them barring the 1st fret, held at the 1st fret.
None of them uses an open string, so this chord moves up the neck unchanged — the same shape 1 fret higher is the chord a semitone above.
1 of the 2 need a barre.
Where its notes are on the neck
The brass dots are A♭, the root. Everything else is a chord tone with its degree printed in it.
With a different note underneath
A♭m6/C♭
4546
A♭m6/E♭
8878
A♭m6/F
abbb
An inversion is the same chord with a different note lowest. The name changes to a slash name because the bass is what a listener hears as the foundation.