Unfortunately the instructions for deleting apps does not apply to this situation. The Mail App cannot be deleted off the Apple Watch without also deleting it from the iPhone and I do not wish to delete it from my phone, only my watch. Perhaps this ability could be added in a future update to the iOS.
Additionally, while I have deleted a lot of other things off the Watch (I only have 4 applications, 21 photos-though I can't figure out where they are as they are not in the photo app-as well as zero songs, per the About Screen), the mail app is taking up 1.1gb of space even though there is no mail/messages on my Apple Watch as I have set it so only one account is showing up on my watch, and that account is completely empty of all mail. I don't understand why the Mail app would take up so much space on my watch, especially without any messages. Currently, 4.8gb of space is used on my watch, while only 277mb is available. I have deleted everything I seemingly can on my watch and yet there is barely any space let. I have restarted my watch and ensured that the iOS is updated to the latest version.
I am going to try deleting all messages from my Apple Watch but another suggestion would be to enable messages to be deleted in bulk from the Apple Watch, or to allow you to delete them off the watch from your iphone.
I could really use help to free up space as with so little on here, I have no space, and no room to add any music or apps.