Slow down entire slide/voice - text to speech

Is there an easy way to slow down the text-to-speech for each slide-to-speech file?

Meaning, I don't want to slow down a specific word or words but rather the entire paragraph of text on a slide. I want to slow down the entire rate for that voice file.

Any way to do this?

It would be nice to have this an option when the "insert text to speech" window opens. Then have a selection to slow down the rate at that point, with options of rate speeds)