How do I delete photos from the watch

The photos are synced to the watch from your iPhone. To remove photos change the album that is synced to a different one without the photos that you want to be removed. You change the synced album in the Apple Watch.app on your iPhone.

See: https://help.apple.com/watch/#/apde3d82be52

Thanks but how do you erase all photos with out syncing another album

Select an empty album to sync. You can create a new album "Erase" with just one photo in Photos and sync that instead of your Favorites album that will have many photos.

I don't actually see a way to remove the photos. You can change the synced album but that's about it. I've set the storage limit to the lowest amount - 5MB. If your album had more than that, doing that will get rid of some.