Place it right after the slow moment peaks, then follow it with a shocked reaction to sell the disbelief, or a goofy yell to turn the wait into a joke. Keep it as the middle beat between the setup and the payoff, not the opening.
このサウンドについて
This short clip stretches out the phrase 'so zetta slow' into a drawn-out, teasing callout lasting just under three seconds. The slow delivery makes it feel mocking and patient at the same time, like someone waiting while everyone else catches up. It works as a light jab at slowness rather than an angry complaint, with the stretched vowels doing most of the work.