Polenta Sliders

Name: Polenta Sliders
Ingredients: Nonstick cooking spray; 2 tablespoons extra-virgin olive oil; 2 large cloves garlic, finely chopped; 1 teaspoon dried oregano; 1/4 teaspoon red pepper flakes; One 24-ounce tube prepared polenta, sliced into sixteen 1/3-inch thick slices; 2 medium tomatoes, cut into eight 1/4-inch thick slices; 2 small red onions, sliced into eight 1/4-inch thick rounds; Kosher salt and freshly ground black pepper; 12 ounces lean ground beef; 24 fresh basil leaves