Create a new document (mine is 600 by 420 pixels) and fill with a dark gradient or solid colour. I’ve filled mine with a radial gradient from #242424 to #0e0e0e.

On a new layer select the rounded rectangle tool and make a rectangle 250 pixels wide and 300 pixels high with a colour of white and a radius of 5 pixels. This is our page

Step 3

Using the polygonal lasso tool make this selection. Hold down the shift key to make it line up at a 45 degree angle.

Step 4

Rasterize the layer (right click > rasterize layer) and remove selection (hit delete).

Step 5

On a new layer use the rounded rectangle tool to make a 100 by 100 pixel white box.

Step 6

This is our fold part, and we want to get rid of the part outside of the page so firstly rasterize the layer like we did before. Now select the area of the page (Ctrl + click the layer’s thumbnail) and invert selection (Select > Inverse) and hit delete.

Step 7

Duplicate this fold layer and fill with a linear gradient from the top right to the bottom left using the colours # and #. This is the fold shadow layer.

Step 8

Go Edit > Transform > Warp and stretch out the bottom left corner. Hit enter to set the transformation.

Step 9

Move the shadow layer below the fold layer (in the layers window by dragging).