Use colour casting and lighting effects to create an imaginary scene
Begin by opening an image of some clouds as your background and rename the layer ‘Clouds’. Then import a suitable rocky, canyon shot onto your canvas and resize it with Free Transform to fit the width of the image. Using the Eraser tool at 100% Opacity, erase everything above the canyon range to extract the mountain.
Using the Lasso tool, roughly select the lower portion of the clouds on their layer and then copy it into place on a layer above the canyon image by pressing Cmd/Ctrl+Shift+V. Use the Eraser tool with a 10% Hardness to reveal the canyon below through the clouds.
Creating parallel horizon lines for the clouds and the mountain range tends to lead to a boring composition. Add more depth to your image by extracting protruding sections of the mountain and applying clouds over them as you did in Step 2 for a little more dynamism in the piece.
You want to add a point of light to the sky as this will make your scene more interesting. Import a sunset image into your document and lower the layer’s Opacity to 50% temporarily as you place and resize the image to the canvas.
Again, use the Eraser tool with Hardness set to 0% and the Opacity at 100% then erase the seam to create a soft blend between the sky and the existing clouds on the image. Take your time here.
Find a suitable image of a castle and, using the Free Transform tool, resize it to sit on the left half of the image, placing it so that the top covers the sun, your light source. Use the Pen tool (or your favourite extraction method) to create points that select the shape of the castle and cut away the excess parts of the shot.
Before compositing a structure made up of numerous building blocks, it can be good practice to draw out the shape of the desired island. Using the Brush tool with the colour set to red for maximum visibility, sketch out the triangular form of the island on a new layer.
Import a stock short of a cliff into your picture. Using the Lasso tool, select a cliffside section of the image and paste it onto a new layer. Then, using a hard Eraser tool, brush around the contours of the cliffside to create a nice, rocky shape. Transform the shape to follow the left side of your sketch using your red lines as a guide.
Continue building up the island by using segments from your cliff shot. A method we employed was to build the outer edges first. That way you can build the base by piling segments on top of each other as you work towards the centre, concentrating on the silhouette before thickening the middle.
Using the same source to build out the island will ultimately lead to sections where the same noticeable patterns appear within the composition. Find the most noticeable of the shapes commonly appearing in your image then select a nondescript section of rock texture and simply place it over these parts to alter the pattern to the naked eye.