Greek Meatball Bowls

Name: Greek Meatball Bowls
Ingredients: 3/4 cup panko; 3 small scallions, thinly sliced (about 1/2 cup), plus more for garnish; 1/4 cup chopped fresh mint; 4 large garlic cloves, finely chopped (1 1/2 tablespoons); 1 large egg, beaten; 1 1/3 cups plain whole-milk strained (Greek-style) yogurt, divided; 1/4 cup, plus 1 tablespoon chopped fresh dill, divided, plus more for garnish; 2 1/4 teaspoons kosher salt, divided; 1/2 teaspoons black pepper, divided; 1 pound 85/15 lean ground beef; 4 Persian cucumbers, divided; 1 teaspoon grated lemon zest plus 1 tablespoon fresh juice; 1/4 cup extra-virgin olive oil, divided; 1 small red onion; 1 1/2 cups uncooked orzo; 3 cups chicken stock; Lemon wedges, shredded romaine lettuce hearts, crumbled feta cheese, kalamata olives, and halved cherry tomatoes, for serving