If you no longer have access to the iPhone paired with your Apple Watch, or if the watch is completely frozen, you can wipe it directly from the watch itself using the physical buttons.
How to Factory Reset from the Watch
- Connect your Apple Watch to its charger.
- Press and hold the Side button (the flat one) until you see the power icon in the top right corner.
- Press and hold the Digital Crown until you see the “Erase all content and settings” prompt.
- Tap Reset and confirm.