OK - lets get started

1. Open your image, press shift D twice to make 2 copies, close your original and minimize one of your copies

2. Resize one copy to around 200 pixels, then apply seamless tiling with the default properties.  Minimize this tile and bring up your other copy

3. Add a symmetrical border of 4 (any colour), click your border with your magic wand, then flood fill with a light colour from your image (note this colour because we will be using it again). Do not deselect

4. Apply FFA Pool Shadow with the following settings

5. Invert your selection and apply the following cutout. Deselect

6. Add a symmetrical border of 4, this time in a dark colour from your image (note this colour because we will be using it again)

7. Add a symmetrical border of 4 in your light colour, click with your magic wand, then apply pool shadow with the settings we used before

8. Add a symmetrical border of 14, any colour, then flood fill with the tile we made earlier, apply a gaussian blur with a radius of 10, then apply pool shadow with the setting we have been using. Do not deselect

9. Apply a cutout using the settings below - changing the blur to 8, repeat with minus values. Deselect

10. Repeat steps 3, 4, 6 and 7

11. Add a symmetrical border of 44 any colour, click with your magic wand then flood fill with your background tile. Apply a gaussian blur with a radius of 10, apply pool shadow with the same settings we have been using. Do not deselect

12. Apply Medhi Melt with the following settings. Do not deselect

13. Apply FM Tile Tools blend emboss with default settings twice. Do not deselect

14. Apply the same cutout we used last, changing the blur to 18, repeat with minus values

15. Repeat steps 3, 4, 6 and 7

That's it - all done!