Preheat the oven to 350 degrees F.

Bring water and rice to a boil in a covered saucepan (or cook for 4 minutes in the Instant Pot). Reduce heat to low and simmer until rice is tender.

Meanwhile, heat oil in a skillet over medium heat. Add ground beef and cook until browned and no longer showing any pink spots.

While the rice and meat are cooking, hollow out bell peppers by removing and discarding the tops, seeds, and membranes. Arrange peppers in a 9 x 13-inch baking dish with the hollowed sides facing upward.

In the skillet, stir together the cooked rice, cooked beef, tomato sauce, garlic, Italian seasoning, red pepper flakes, and salt and black pepper to taste. Spoon an equal amount of filling into each hollowed pepper.

Bake for 35 to 45 minutes, or until the peppers are tender. Remove from the oven, top with shredded cheese, and return to the oven. Bake until the cheese is melted; about 7 to 10 minutes.