Ext. Back Cover Editing - Photoshop

To make the back cover match the front covers theme of glitches, I decided to add a subtle 3D effect to the background image. 

I began with the existing back cover then duplicated the background image twice. 

I then right clicked on the new layer and selected 'Blending options' . From there I deselected the ticked G box.

 

I repeated this on the 2nd new layer but instead of deselecting the G box, I deselected the R. 

I then proceeded to click the left arrow on my keyboard to shift the layer to the left. This created the 3d effect as the red and green colours showed through.