I thought my new Block Templates would look good as a double layout so I'm going to show you how. Seriously it only takes 1 step!
First you'll open the template and save it with a new name so that you don't save over the original template. Then all you have to do is go to Image>Rotate Canvas>Flip Canvas Horizontal. That's pretty much it. You will have to remove the journaling and title layer since they will be backwords but you'll have the basic template and you can easily copy the journaling and title layers (from the original template) on to the new template and place them where you would like. This way flips/rotates the whole canvas. Keep reading to see how to flip/rotate individual layers.
Here's another way to do it if you only want to flip a couple of layers. (Select the layers you want to flip (hold down ctrl + click on all the layers you want to flip/rotate) then go to edit>transform> and then you can either go to rotate 180, rotate 90, rotate90, flip horizontal, or flip vertical. Sometimes it's fun to play around with the different layers so that you can get a similar but not completely flipped layout.