URLs can contain custom values to automatically set timer values. The hours, minutes, and seconds parameters are used to set the timer. The ! parameter disables confetti. The ~ parameter disables audio. Embedding certain names within -- shows customized logos.
To embed the timer in a Powerpoint presentation, you can use the Web Viewer add-in.
Disclaimer: Play around with this before you add it in your presentation, the add-in is not very customizable. It is best to place the timer in the bottom right corner of your presentation, slightly off-screen so as to hide the frame of the plugin.