Books about “how to create comics” often talk about the two ways to write a comics story: “full script” and “plot first/Marvel-style.” These discussions leave out a third method.
Throughout the past century thousands of comics scripts have been generated by sketching the pictures on the page and handwriting or typing the dialogue on it. You can see a dramatization of Harvey Pekar using this method in the movie American Splendor. According to Mark Evanier, this script method was common practice in funny animal comics, and at Western (a.k.a. Dell, Gold Key, Whitman). At times, Archie Comics has required writers to provide thumbnail sketches of page.
Michael Barrier has posted a terrific look at a 1948 Porky Pig script by Chase Craig on his blog. It’s a fascinating look at the creation of a classic era comic book story. Check it out.