The resource center Robert mentioned is very good.
There is a couple of videos on Voice Bots, just note how it handles intents is different to digital bots.
But has some good info around design, slots etc.
https://www.youtube.com/watch?v=6dX44UWyP14
https://www.youtube.com/watch?v=02rHUCIDnEg&t=5s
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Anton Vroon
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