Toast the bread.
Spread mayo on one side of each slice of bread. Layer with arugula, spinach, tomato, turkey, provolone cheese, cucumber, onion, and pepperoncini. Drizzle with olive oil and season with salt, pepper, and oregano. Place the sliced avocado on top.
Top with the second slice of bread, mayo-side down. Press gently to secure the sandwich, then slice in half.
For the lemonade, mix the lemon, water, and sugar to taste. Serve over ice if desired.
Serve the turkey sandwich with potato chips and homemade lemonade. Enjoy!