My dog is large with an unusual body shape, by the way. There aren't a lot of pre-made patterns out there in her size.

try net-searching "livingsoft software" they have computer program that allows you to custom design/ fit patterns. Years ago their news letter talked about they were considering creating a line for pets.

I didn't have the money then and I have been out of the sewing mood for a few years. Hope it might lead you somewhere useful.

I have two dobermans and last year I made them winter coats. I did buy a couple of patterns but I didn't use them. I did have a winter coat that I bought so I made a pattern with that coat. I added a tummy warmer and a long collar to keep their neck warm on those cold winter days. I'm also a novice sewer. It took me a while to make the two patterns but it worked.

I think you might want to try your local library - see if they have any books on pattern drafting - or even books about making pet 'clothing'...

You might also try buying a pattern & tracing it onto sturdy paper, so you can play around w/it.

I was going to try to explain how to make a pattern from scratch but it may not work well for a dog as it would for a person since doggies don't stand still. Plus it is a lot of free hand drawing and cutting muslin then fitting and recutting. So my best suggestion when someone asks me how to do this and they don't sew a lot is use an old shirt, dress or skirt. You can de-construct a piece of clothing then transfer it to muslin and or paper. You said she has a unusual body shape so if you have one outfit that doesn't fit quite right that would be the one to use. Another suggestion if you don't have any outfit for your dog now is to buy people clothes to fit her. A thrift store is good. You can buy a boys or girls tee shirt and even some pajamas would work. You can adjust it large, small, longer, or even shorter. You will put the shirt or coat on the dog inside out. You couldn't pin it since you will need to pull if off the doggy and she may get stuck! Not good so I would recommend instead of pinning is just pinching the fabric up at the seams where it needs to be smaller and draw a line by your finger on each side with a marker. If you need to add to the area/seam to make it bigger you will have to guess a little and mark next to the seams +1/2" or whatever extra you need. If it needs to be longer measure and write how much you need to add or mark a line where you want to shorten it plus 1/2" for seam allowance. Next you then will just rip the seams out or if you choose to cut the seam then add a 1/2" seam allowance to your pattern. Iron the all the pieces flat. You will lay the pieces out on a paper or muslin. Next you will have to free hand the lines of the pattern if making it larger or just cut the shirt piece in where it needs to be smaller. I prefer to cut out my pattern on muslin first then sew it all together with a long stitch. One suggestion is to cut the muslin pattern with a seam or opening on the back of the dog if a pullover shirt. That way it's easy to put on your dog to check the fit. Muslin doesn't stretch and it would be hard to pull on but you will get the over all fit of your pattern. Once you have the fit you like with the muslin repeat as you did before mark the seams and length then take out the stitching recut the pattern to the adjustments. Now finally you can lay it down on paper and cut out a permanent pattern. I use a drawing paper that comes on big rolls. It's a little stiffer than regular paper plus it will last forever. If you make a full length with sleeves pattern first then you have one you can trace and make different cuts from. Example if I was to make a A Line dress pattern I would make a full length long sleeve first. I could then copy that pattern to another piece of paper adjust it maybe to knee length and no sleeves for the same person. My best tips are the neck opening, arm opening and arms are always tricky. If enlarging you will need to taper in each depending on the look or style you are going for. Remember to add fabric allowances if using non stretchy fabric. The first cut of a pattern alway's go a little larger then adjust. Don't forget the seam allowances. When using a shirt for a pattern they are already there except when you reduce your pattern. When you are pinching the area smaller mark it at the pinch but then note you will have to add 1/2" seam allowance to that area and if enlarging you will need to also add the seam allowance. Several fittings are best. Oh, don't forget the seam allowances it's the best advice I can tell you over and over. I tried to write everything as I do it step by step. But if not clear or any questions let me know. Have Fun and Good Luck!