Folded corners or edges
Note from Pat
For this example above you will need two layers of paper or two different colours or patterns.
Follow steps 1 to 4 as shown in the example above - cutting and pasting the pieces onto a new layer each time.
Once everything is in position - (I have used lines to show the pieces up)
Then you can start applying shadows and use the warp tool or warp brush to alter the fold slightly.
Experiment
Take a real piece of paper and fold the corner down and up again and see how it lays.
If it is soft paper or tissue it can stretch slightly it may even curl a bit.
Instead of using negative image to change the colour of your first cut piece, try colorizing it.
See another example tutorial here at Corel.com Tutorials.