After each step, if there is an OK button to click in the dialog boxes, click it.
1. Launch the GIMP and create a new file. Make sure it has a decent size - all from 512x512 up to the megalomaniacal 4096x4096 can be done... even though that is a bit much, since the framerate drops with detail. Fill it with white.
2. Use the Filters > Render > Clouds > Solid Noise... filter. Tick Randomize and untick Turbulent. Set Detail to 5 and both the sizes to about 4.
3. Apply Filters > Blur > Gaussian Blur (RLE)... and set the sizes to a value between 5 and 10. This smoothens the clouds a little.
4. Open up Tools > Color Tools > Brightness-Contrast... and set the Contrast slider to a number between 100 and 127. The program generates a preview anytime you change the value, so you can see how it should look like. I mostly use 120. The picture may now look a bit extreme, but that will change soon.
5. Activate the Filters > Colors > Colorify filter, clicking custom color and setting the sliders to a value of about FF9E00 in hexadecimals - a shade of orange.
6. Use Layer > Colors > Invert.
Lookin' nice, eh?
7. Save your file. I don't care where.
