Begin the project with a large white poster board, either foam or cardboard, as your canvas. Choose a size according to your need. Lightly sketch with pencil onto the poster board the projected placement of your elements.
Trim out photo elements, eliminating all background imaging, either in Photoshop prior to printing or by carefully excising the image with scissors.
Paste at least two or more images onto heavy construction paper. Trim them out carefully. On the back of these images paste large foam squares, 1/2-inch thick foam on the first image and 1/4-inch thick foam on the second image. This effect can be applied to a variety of images at different depths, but keep in mind that larger images projecting farther out of the poster imply that they are closer to the viewer or larger in scope.
Apply paste to the foam on the back of the first image, and adhere this to the top of the poster board, with 1 inch of the image projecting above the poster board and 1 inch projecting outside the poster board on the left side. Affix the second image in the same manner at the bottom-right side of the poster board.
Add in a text portion of the poster, in very large letters, making certain that the text does not overwhelm or overshadow the images. Center the words, one below the other, large and placed appropriately for the overall image of the poster.
Paste the text box with all the information you wish to convey on the lower-left side of the poster board. The large 3D images will capture the eye of someone standing far away from the poster and draw the viewer closer to read your information.
Paste in other photographic objects such as smaller objects, or slightly blurred objects to imply greater distance, that sink far back into the poster. Be certain to add a drop shadow in Photoshop, so that some of these images stand out from the background, providing a 3D illusion even among the "pop-out" pictures.