Advice for Making Foo Creatures / Any Creature

[Vyranos]

You guys know the Foo Dog and Foo Lion in the Bestiary 3, right? Well, I want to make my own Foo Creatures (so far, I'm thinking on a Foo Cobra), and, while the book has a technique to tell you how to make one, there's one problem...

I've never made my own Creature before.