Place it at the peak of the mishap, just as the fall begins, then follow it with a hard impact thud so the gag lands with a finish. For a bigger reaction, open with a shocked gasp before the yell, and close with a laugh once the dust settles.
About this sound
This is a short, wavering cartoon yell in the style of Disney's Goofy, lasting about two and a half seconds, with a high, stretched cry that rises and wobbles as if its owner is tumbling through the air. It feels instantly silly and slapstick, turning a simple slip into a big, exaggerated disaster before anything even lands. The sound is tied to Goofy's clumsy screen persona and his falling gag.