Why are you using slow talk? Please do NOT use it if it makes you uncomfortable (although, I am not sure how this could be possible). Slow talk should ALWAYS be a pleasant, calming thing that you use IF you feel anxiety rising (adrenaline rising). There is no need to use slow talk unless you are anxious or panicked.
So, if you are anxious your talk will be starting to go faster (the adrenaline causes this to happen). Slow it down. Don't let the adrenaline take over. Calm it down. That's all calm talk is.
Again, there is no need to think about calm talk unless you feel anxiety coming on. Then, just remember NOT TO SPEED UP. That is all that calm talk is.