+1 for Clockwise, it does a great job of automating this. It easily doubled my team's work time ("focus time" in Clockwise).

It also has useful preferences like "prefer morning/afternoon", "no meeting days", which it takes into account when scheduling.

I can't say enough good things about it. It's free at first but I would pay almost any money to keep it, the value of the extra time it gives you is enormous.