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This isn't a comic strip, it's prose. Written this way, the slap seems cartoony. I'd much rather you describe the action than simply recite the sound it makes.
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#3: Attribution notice added
Source: https://writers.stackexchange.com/a/25606 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/