In the above layout, the foot extends out of the picture, overlapping the background. To achieve this effect in Photoshop:
- Duplicate the layer.
- Select the upper layer (by clicking on the appropriate layer in the Layers Palette) and extract the part of the photo that will overlap the background (in this case the foot). To see only the extraction, turn off the bottom layer by clicking the eye in the layers palette. If the extraction is suitable, click the eye to turn the bottom layer back on.
- Select the bottom layer and crop it into the shape you want it to be. In this case I used the Rectangular Marquee Tool, dragged my mouse over the part of the photo I wanted to keep, then clicked Select > Inverse, then I chose Edit > Cut.
- Optional: Next, I added a stroke to only the bottom layer (Layer > Layer Style > Stroke).
- Optional: At this stage, if you wanted to add a drop shadow, it would be best to merge the two layers (select both layers in the Layers Palette then choose Layer > Merge Layers).
Navigate to the next page for another example of an extraction overlap.