Make a new document, 1000x1000 pixels, white background
On a new layer, make a shape with the polygonal lasso tool, something like this:
Duplicate the layer and right click on the shape, free transform and then flip horizontal. Now move the shape until you get a new nice shape. Here is mine:
Merge the two shape layers and repeat the steps above, but now flip the shape vertical. Now you'll have something like this:
Merge again the two layers and repeat the steps but now you'll have to flip the shape 90 degrees. Now this is what you'll get:
Now add a "drop shadow", "inner shadow", "outer glow", Bevel, satin, pattern overlay, whatever you like until the result will suit you.
