Pat the beef cubes dry with a paper towel and season them with the sea salt and black pepper.
Heat the olive oil in a large heavy-bottomed pot or Dutch oven over medium-high heat.
Add the beef to the pot in a single layer and sear until browned on all sides, then remove the beef and set aside.
In the same pot, add the diced onion, sliced carrots, and celery, sautéing for 5 minutes until the onions are translucent.
Stir in the tomato paste, dried thyme, and dried rosemary, cooking for 1 minute to wake up the aromatics.
Pour in the beef broth and use a wooden spoon to scrape up any browned bits from the bottom of the pot.
Return the beef to the pot, bring the liquid to a gentle boil, then reduce heat to low and cover with a lid.
Simmer for 45 to 60 minutes, or until the beef is very tender.
Add the trimmed green beans during the last 10 minutes of cooking so they remain bright and slightly crisp.
Ladle the stew into a bowl and serve warm.