SOAK INSTANT RICE: In a small bowl mix together the uncooked instant rice and chicken stock or broth and let stand for about 10 minutes. You do not need to pre-cook the rice. Don't drain either.
OVEN/GRILL PREP: Preheat the oven or grill to 400 degrees F. Tear off four sheets of heavy-duty foil (about 2 feet long each) and generously spray with cooking spray.
INGREDIENT PREP: Very thinly slice the celery, finely chop the onion, dice the pepper, and coin the zucchini into thick (3/4-inch) coins. Slice the sausage into 1/2-inch thick coins. Drain the diced tomatoes.
COMBINE: Add the celery, onion, pepper, zucchini, and sausage to a very large bowl. Add the tomato paste and drained diced tomatoes. Add all the seasonings as well as salt and pepper to taste (I add a heaping 1/4 teaspoon and 1/8 teaspoon pepper). (See Note 1) If you'd like, add in a diced jalapeño for additional heat. Gently stir until all ingredients are well combined. Add in the soaked rice along with any liquid. Again, gently stir until ingredients are incorporated.
ASSEMBLE FOIL PACKS: Divide the mixture evenly among the four prepared sheets of foil. (This comes out to a heaping 1 and 1/2 cups (330g) per packet.) Seal the foil packs tightly so no air escapes, but there is still room for steam to circulate. (See Note 2) To seal the foil packet, bring the short sides together in the middle and gently fold down to completely seal. Then, roll up the ends.
COOK: Place in the oven (right on the oven racks) and bake for 30-40 minutes (we like them best at 35 minutes) or on the grill for 25-30 minutes, until rice is cooked through and veggies are tender. (Test only 1 packet at a time; every time the packets are opened, the steam is released so it will take longer to cook.) When grilling, flip packets halfway through cook time.
GARNISH: Carefully open the foil pack, expecting steam to be released. If desired, top with fresh parsley. Let slightly cool, taste, and add additional seasoning as needed. Enjoy hot.