Multicooker Directions: In Step 1, transfer the remaining onion mixture to the inner pot of a 6-quart multicooker. Stir the stock, carrots, zucchini, green beans, celery, and tomatoes into the pot. In Step 2, carefully submerge the meatballs in the chicken stock mixture in the pot without stirring. Lock the lid; turn Pressure Valve to "Venting." Cook on SLOW COOK [More] until the meatballs are done and the vegetables are tender, about 3 hours. Finish Step 2.