Put it just after the awkward line, before a Vine Boom Sound Effect, then let the next beat play out. For a bigger fail, follow it with a SpongeBob Fail Sound Effect instead of stacking both at once.
About this sound
This is a brief burst of chair noise, lasting about three and a half seconds, with a thin squeal that bends and wobbles as wood scrapes under weight. It lands as awkward and funny at once, turning a small shift in a seat into a moment of exposed embarrassment that listeners recognise instantly from classrooms and offices.