F7sus4/Bb (F 7sus4 over Bb)
Notes, from the bass up
Bb (bass)CEbF
A slash chord names two things at once. The part before the slash is the chord your right hand plays, and the part after it is the single bass note for your left hand. Read F7sus4/Bb as F 7sus4 with Bb in the bass.
The bass note here is one of the chord tones, so this is exactly the 1st inversion of F 7sus4, written the way sheet music and chord charts usually write it.