Callum Joy created a book cover design and documented the process. They added background images and removed white space from rats. Text was added for the title and details, and images were overlapped to create a collage-style layout. The design process involved testing fonts, adjusting images and text, and adding elements like barcodes. The final cover featured a woodland scene with rats and was laid out across a double page spread to showcase the book's subject and provide descriptive details.