*Note*
All Images are scaled to 500%. The actual size is way too small for this page, so just keep that in mind.
Step 1 - Starting Out
Create a new 18x12 document. Create a new layer, and create a 1px black border like in the image. This will be the border layer, and it will never be modified through the rest of the tutorial.
Step 2 - Green Block
Create a new layer and place it between the background and border layers. Next, since I will be using Italy in the example, fill in a nice 5x10 block of green with the 1px pencil tool (or alternatively, used a fixed marquee tool size of 5x10 px, and just fill it in with the paint bucket tool.) Make sure the green color is pure green (#00FF00).
Step 3 - Red Block
On the same layer, do the same thing for the right side of the flag. Make sure it is a pure red color this time (#FF0000).
Step 4 - White Block
Fill in between the red and green blocks with white. This step is required as blending options might not work properly unless the rest of the space is filled with the proper color (white in this case.)
Step 5 - Blending Options
Right click the green/white/red block layer, and enter the blending options. Follow the image for gradient overlay...
If you did it right, it should look like the image below. What were trying to achieve with the gradient overlay is just a color enhancement. Gives more detail to the flag in the end.
Step 6 - Gloss
Next, create a new layer above the green/red/white block layer, and selec the gradient tool. With a white to transparent gradient selected, click and hold the tool at the top of the image, and drag all the way to the bottom. The white gradient should give a glossy effect like the image below.
Step 7 - Final Comments
That's it! Simple tutorial, but with an amazing flag. This flag is perfect for any forum skin you're planning to build. Also, what's great about the scheme of this PSD is that to change the flag, all you have to do is fill in the correct colors with the pencil tool. The gloss and gradient overlay will already be added into the image. The final result scaled to 100% can be found below.
End! Job well done! :)