[Yukino]

https://www.youtube.com/watch?v=WZe-GBtmJCM how do you do the slash effect to seperate photos from each other
more examples http://prntscr.com/ggq7iv
Thank You!

[Blue Shadow]

Put the images where they need to be.

Use the pen tool to select the image that will be cut off (the larger one usually)
warning large image (Click to View)

Then right click the image with the pen tool out and hit make selection.

Switch to the rectangle selection tool and right click the image > make copy from selection

Delete the original layer and keep the cropped layer

optional way (Click to View)<< [this method to cheat a little or use rectangle part below] now right click the layer > blending options > stroke > set it to outside > make width/color what you want [or use method below]
Spoiler (Click to View)
(you could also use pen tool > stroke > brush for this but that can be confusing for a beginner



Make a rectangle at the width you want using the rectangle tool. it doesnt matter the orientation.

Rotate the rectangle to be at the same angle as your cropped layer's cut

Drag ends of rectangle so it goes across the whole cut

Lastly, profit?