In a very large lidded pot (I used a 9-quart dutch oven), warm the olive oil over medium-high heat.
Add the onions, celery, and carrots and sprinkle the salt overtop. Cook, stirring occasionally, until the vegetables start to get tender and there’s plenty of nice browning on the bottom of the pot.
Add the garlic and cook, stirring a couple of times, for one minute, until you can really smell the garlic.
Add the tomato paste and cook, stirring constantly, for a minute more.
Pour in the stock and diced tomatoes. Add the thyme, oregano, and red pepper flakes. (If you're using the parmesan rind mentioned in the notes, add it now). Stir and scrape up all the browned bits from the bottom of the pot. (You won’t be able to see them, but you can feel the difference with your spoon.) Bring to a boil over high heat.
Add the potatoes, zucchini, green beans and canned beans. Reduce the heat to maintain a gentle simmer, cover, and cook for 10 minutes.
Add the kale and cook about 10 minutes more, until all the vegetables are tender.
Off the heat, stir in the basil leaves.
Ladle into bowls and serve, with grated (vegan) cheese to pass at the table if you like.