Is there a video tutorial to making seamless skyboxes?

I need to know how to make a skybox for my game in unity, something that isn’t rough around the edges, fits in nicely like the free pre-made skyboxes that can be downloaded with unity. I’ve looked around and couldn’t find anything to show me exactly how step by step. Any help is appreciated.

I recommend you to use gimp with tileable function , here are a example , if you put this image in four walls , the top blue and the bottom white , you will get a seamless skybox

alt text