Slow Cooker Ribollita

Name: Slow Cooker Ribollita
Ingredients: 1 pound dried cannellini beans; 2 tablespoons extra-virgin olive oil; 1 large sweet onion, small-diced; Kosher salt; 2 large carrots, small-diced; 3 celery stalks, small-diced; 1/2 large butternut squash, peeled and small-diced (2 cups); 1 head garlic, cloves separated, peeled, and thinly sliced; 1 (28-ounce) can San Marzano tomatoes, drained; Bouquet garni: 2 bay leaves plus a couple sprigs each of fresh sage, oregano, flat-leaf parsley, and thyme, tied together with twine; 1 tablespoon crushed red pepper flakes; 1 pound cavolo nero (a.k.a. dinosaur kale or Tuscan kale), leaves torn into small pieces, stems finely minced; 3 cups torn country bread, toasted; 1 1/2 cups finely grated Parmigiano-Reggiano cheese; 6-quart (or larger) slow cooker