For months, that’s how I wrote my first book, and then my second book. Some days the words were like a thundering river, literally gushing onto the pages. Other days, it was more like a seasonal creek in the middle of a long drought. I was lucky if two coherent words trickled out. Mostly, I ended up just looking at a blank page. I didn’t know it at the time, but I was a Pantser.
So, you’ve got an idea for a book? Fabulous! It’s a work of SciFi/fantasy, you say? Awesome! Ah, and I see you’ve got a list of characters and a general plot of your story. You’re doing great! Now what about a worldbuilding outline?