Reset watch
How do I reset my Apple Watch to factory settings?
Apple Watch Series 3, watchOS 8
User profile for user:
Community User
Unpair and erase your Apple Watch
Or;
To unpair and erase watch and remove Activation Lock
From a web browser,sign in to iCloud.com with your Apple ID.
Go to Find iPhone.
Click All Devices at the top of the screen.
Click your Apple Watch.
Click Erase [device]. Select Next until the device is erased.
Click Remove from Account.