First, I drew an outline of my hand on a page of the Wall Street Journal. You can see that the paper is well worth the subscription price - I can use it for multiple things! I wanted the mittens to go several inches above my wrist, so that's how I traced it. However, I gave it more ease above the wrist (drew the line farther away from my body), to allow for the arm being thicker than the hand.
I placed the paper on the fleece and drew a chalk line about 1/4 to 1/2 inch away from the paper's edge. I was lazy and didn't pin the paper to the fleece. I drew and cut out four, two with the thumb to the right, and two with the thumb to the left. Then I sewed the fleece pieces together and used the fleece undermitten as the guide for cutting the sweater. This time I did pin the undermittens cutting guide to the sweater, and cut 1/2-3/4 inch away from the fleece edge on the wool.
I sewed the wool pieces together, turned them outside out, put the fleece inside - put my hand inside - and voila! An extremely warm fleece-wool mitten for those awful winter mornings when I have to scrape off the car to go to work. I may tack the fleece and wool together in a few places and clean up the wrist a little, but altogether, this project took maybe an hour at most. Extremely quick and cheap project!