You only need to measure/cut three pieces. For the top and bottom, just trace around the lid, and cut a *little* larger than this. For the body, measure around the perimeter/circumference of the pot, plus the height. Add a *little* extra to these as well (the final length should perfectly match the outside path of your bottom piece), then tape together the bottom with the main body and you should be good to go.
BTW, depending of the brand of noodle you use, you can often put the noodles into the cold water, bring to a a boil and eat without further cooking. A cozy is not always needed..