My watch face is upside down. How do I reverse it

Go on your iPhone, go to the Watch App, then go to General. From there, go to the Watch Orientation and you can determine the settings to get the Watch oriented correctly.

First, you have to configure the Watch orientation.

Are you wearing the Watch on your left or right arm?

Do you want the Digital Crown on the left or right side?

You can configure Watch orientation using your paired iPhone:

iPhone's > Watch app > My Watch > Watch Orientation > do it here

After that your watch face will have the correct orientation.