Bb 3/F#
The Bb 3 chord consists of the Bb (Perfect unison) and D (Major third) notes, with F# as the bass note.

How to play the Bb 3/F# chord
- Play F# as the lowest bass note in the left hand
- Find Bb (Root) on the piano keyboard
- Add D (Major third) — 4 semitones above Bb
- Press all 3 notes simultaneously to sound the Bb 3/F# chord