When my friend Caroline got a new little dog, one of the first things she asked me was for a jumper for the winter.
I can’t remember which pattern I used, but it involved a lot if Internet searching to find it. Essentially this is knitted flat, the width is the dog’s waist measurement. The length is slightly different. Whilst holes are incorporated for front legs, the back legs aren’t in the jumper. Therefore, assuming seam goes underneath, you would need to cast off some stitches leaving a panel the width of the back and continue until the jumper measures from bottom of neck to top of tail.
I used an own designed but basic cable pattern all over.
Update: found the pattern!