https://techcrunch.com/2023/01/17/googles-clock-app-now-lets-you-record-your-own-alarm-sound/

Google’s clock app for Android has plenty of sound options to set as an alarm. If you don’t like the default tone, you can use a song or a podcast from Spotify or YouTube Music (only if you have a premium subscription), too – and Google now also allows you to record a voice clip and set that as an alarm tone as well.

This feature was first noticed by Esper.io’s Mishaal Rahman. As he noted, this is a server-side push, so as long as you are using Clock app version 7.3, you should see this feature without updating the app.