Thanks for all of your kind comments. I really was nervous about posting a layout!
To create this, I basically just used the Custom Shape tool to draw a frame around the part of the picture that I wanted to keep "in the box" or 2-dimensional. Then under Image > Transform > Perspective, I dragged the corners of the frame to achieve the desired effect. When you change the Perspective, that is what makes it really look 3-D, in my opinion. Then I erased the part of the picture that was outside of the box and that I didn't want to keep. I also erased the top part of the frame where the hand was coming out of the picture. The reflection or shadow was already in the picture, luckily, so I didn't have to try to create that!
I hope these instructions make sense. I'm not used to telling people how I created a page.
I made this page of my niece's hand using PSE 2 and the "out of bounds" technique. It is not the first digital layout I've done, but it is the first one I've posted in a setting like this. (Please be kind!)