Navy Bean and Escarole Stew with Feta and Olives

Name: Navy Bean and Escarole Stew with Feta and Olives
Ingredients: 1 head of garlic, cloves separated, divided; 6 tablespoons olive oil, divided, plus more for serving; 1 medium onion, chopped; 1 small fennel bulb, chopped; Kosher salt; 1 tablespoon finely grated lemon zest; 2 teaspoons finely chopped rosemary; ¾ teaspoon crushed red pepper flakes, plus more for serving; 2 bay leaves; 2 cups dried navy beans, soaked overnight, drained; 8 ounces feta, preferably in brine, brine reserved, cheese crumbled; 4 large sprigs basil, plus leaves for serving; 1 cup Castelvetrano olives, pitted, torn; 1 head of escarole, leaves torn into 2-inch pieces; 3 tablespoons fresh lemon juice; 4 1-inch-thick slices country-style bread