In a large mixing bowl, combine the ground turkey, chopped spinach, diced bell peppers, crumbled feta cheese, finely chopped onion, minced garlic, breadcrumbs, red chili pepper flakes, and fresh herbs. Season generously with salt and pepper. Mix gently until just combined.

Divide the mixture into six equal portions, shaping them into burger patties about ¾ inch thick. Make them uniform for even cooking. Optionally, create a small indentation in each patty's center.

Preheat your grill, skillet, or griddle over medium-high heat, ensuring it reaches about 400°F. If using a skillet, add olive oil to prevent sticking.

Carefully place the patties on the hot cooking surface and cook for 5-7 minutes on the first side until golden-brown. Flip and cook for another 5-7 minutes until the internal temperature reaches 165°F.

Remove the burgers from the heat and let them rest for a couple of minutes. Serve on buns or lettuce wraps with your favorite toppings.