Star with basic blocks to build up your castle. Drawing as if you're looking up at the castle is a great way of making it look like it's floating.

Use the guides purely for basic form and perspective, elaborate on the basic shapes, in this case by adding pointy towers.

Draw a basic outline of a rock. Think of it as an upside down mountain. Add crevices using sharp angles lines.

Finish off your floating castle with some fluffy clouds encircling the rock.

