Why, what, and how are deeply interrelated.
Our why, what, and how aren't always determined in a linear process. The answers to these fundamental questions may change from moment to moment.
Your why may be "because you want this checked off your to-do list" or "because you want to play with certain materials or ideas."
Your resulting what might be to "start making the first thing that comes to mind."
They may not be lofty in intent, but the intent has been stated. These are valid answers to why and what that will serve as a guide for how you define what is good. Your actions will be the result of your answers.
How long would you spend on a task without understanding why it's important or what you are actually accomplishing? Constantly answering these basic questions are a big part of our everyday life.