Bring the 4 cups of water to a boil in a large saucepan. Stir in the rice, cover and simmer until all the water is absorbed, about 40 minutes. Remove from heat then fluff with a fork. (For best results, place rice, lightly covered, in the fridge overnight to dry out, but this step is not necessary.)
Heat 1/2 the oil in a large frying pan, electric frypan or wok at 200 degrees C. Stir in the carrots and onions then saute until onions begin to soften. Add the garlic and saute 1 minute more.
Stir in the rice, adding oil and stock as needed to keep the rice from sticking. Stir in the peas, celery salt and garlic powder. Cook, stirring, until peas are cooked. Season with tamari to taste.