Procedural materials for cloud formations?

If there's a way to procedurally generate a material based off my own texture please inform me because I'm not aware of it, as I'd like to use my own textures to do the below.

I have been searching through every piece of documentation trying to figure out how I can procedurally generate clouds.

I thought about ping ponging the material scale, but if that isn't the way to go how can I go about this? I'd like to make the clouds look like they're growing, spreading, and rolling across the sky (storm clouds); similar to UniSky's. I know it's procedurally generated, but how? I'd like to understand the concept and learn it.