HOW TO: Delete Layer "Addition" Lines

On my example below, I have added a mask to my paper and added the paper to my canvas. Clearly, you can see the "addition" lines all around the new layer.

If you were to add a drop shadow now, it would be cut off slightly, due to the frames around the layer. You may still want to delete the frames when continuing your design at some point, just to get your footing with your creativity. Here's how to do this:

Go to Edit > Deselect:

Now, as you can see, the frames are gone! Easy! I love it!