I took this pattern, because it's Winter and I wanted the under area. Then I changed it to become longer, with an added layer of polar fleece, and a layer of water resistant fabric, I split it up the all the way up the back back with velcro closure top to bottom, lace at the bottom, and lace neck line, with a belt all around for extra security for the two loops I added to hook Katy's leash unto. Then I made another. It's an easy pattern to use, and it's easy to adjust the size. I will have to get photos.
https://www.instructables.com/id/Hom...For-Beginners/