watchOS 6 added the Voice Memos app. To use it, tap on the Digital Crown on your Apple Watch to see your apps, then:
Choose the Voice Memos app.
Choose Tap to Record.
Record your message.
Tap the End button when you’re done recording.
To find and listen to your recordings:
Tap the Voice Memos app.
Click on your recording in the app.
Tap the Play icon to listen to your recording.
Select the forward or back button to move your recording by 15 seconds.
Tap the delete button to delete the recording.