This is a template I made for all those people out there that need a little help with skybox’s download this archive
Make sure you have guides locked and showing, follow the directions in the template which are on a separate layer for you to use, so you can just turn the on and off. On OS X cmd-; turns the guides on and off, which is handy for when you are merging the seams.
IMPORTANT bit of information: when you use the rectangular marquee selection tool when the guides are on when slicing each view into a separate file, for some reason you want to flip everyone of the orthographic views horizontally accept the left view. I don’t really know why, but the text will show up backwards if it’s not flipped horizontally, and for some reason the left view doesn’t need to be flipped. It’s strange, then just make a CubeMap in Unity and attach it to a skybox!