Attached are a couple items one might use for an ugly sweater design that are completed and can be edited/enhanced. Each color is a spot color and has an underbase built in with registration and should be ready to print to films. There is a top white to help make the bright white areas as well.
With this, you will see there are live pattern fills of the spot colors (with the underbase on each) so that you can use those in other art elements you might create yourself.
To improve the pattern fill and achieve a more realistic "stitch look", you might try expanding the fill and editing out the outer edges that do not make a complete stitch. I got a little lazy in the end and left it up to whoever might want to use it or, you can leave it as is.
The best part of the pattern fill is that since it's live art, (live patterns) you can scale them up or down. Just uncheck the OBJECT and be sure to check the PATTERN in the scale options.
Enjoy...and Merry Christmas!