CGMatter has a look at making procedural volumetric clouds with Blender 2.81.
There are many ways to create clouds, but perhaps the most efficient is to adopt a parametric workflow. Check out this new tutorial from CGMatter that shows how to develop procedural volumetric clouds in Blender in a snap.
The tutorial uses a volumetric material rendered with Eevee. A volumetric sphere goes in a cube, making some adjustments to the shape, lighting it, and adding some procedural noise to get it to look like a cloud.