How to play a Bb7b5 chord on Accordion

AKA: Bb7(b5), Bb7/b5, Bb7(-5), Bb7 Flat 5, Bb Dominant 7th b5, Bb Dominant Seventh Flat Fifth

Notes:

B♭, D, F♭, A♭

Intervals:

R, 3°, dim5°, m7°

Left hand:

B♭ + F♭7
(A# + E7)

Fingering:

2 + 5 (bass pattern)

or

3 or 4 + 2 (counter bass pattern)