For this tutorial, you will need a tube of your choice, the diamond tube, the Corners 1 font, and a silver tile.
1 Open a new image, size 500 x 380 (sides have to be a multiple of 20). 2 Select a sunburst gradient with a dark color from the tube in foreground and a lighter color in background. Fill in with this gradient. Paste in your tube as a new layer. Effects 3D effects Drop shadow : 0/0/60/20/black.
3 Selection Select all. Selection Modify Contract : 2 pixels. Selection Invert. Flood fill the selection with the silver tile. Adjusts Sharpen Sharpen. Deselect. 4 Image Add borders : 20 pixels, very dark color of the tube. 5 Open the diamond tube. Find the layer with the round diamond. Edit Copy. Edit Paste as a new image. Image Resize to 20 x 20 (this is why your image needed to be a multiple of 20). Put this tube as foreground. 6 Select the dark border with the magic wand. Flood fill with the diamond tile. Deselect. 7 Image Add borders : 2 pixels, white. Select that border with the magic wand. Flood fill with the silver tile. Adjust Sharpen Sharpen. 8 Image Add borders : 40 pixels, white. Select with the magic wand. Flood fill with the linear gradient set at 45°, 7 repeats.
Deselect.
9 Image Add borders : 2 pixels, very dark color. 10 Image Add borders : 2 pixels, white. Select that border with the magic wand. Flood fill with the silver tile. Adjust Sharpen Sharpen. 11 Select the text tool, Corner 1 font. Put the very dark color in background. Type in the letter « L » (or any other you want), size 100. Effect Simple filter Top left mirror. Now the four corners are perfectly in place. 11 Sign. File Export JPEG optimizer. | 
