Toast the sourdough bread slices until golden brown.
Spread mayonnaise on one side of each slice of toasted bread.
Layer the bread with arugula, baby spinach, tomato slices, deli turkey, provolone cheese, cucumber, red onion, pepperoncini, avocado, then drizzle with olive oil and sprinkle with salt, pepper, and oregano.
Place the second slice of bread on top, mayonnaise side down. Press gently to hold the sandwich together and slice in half.
To make the lemonade, mix fresh-squeezed lemon juice, water, and sugar in a pitcher until sugar dissolves. Taste and adjust sweetness if needed. Serve over ice cubes.
Serve the sandwich with carrot sticks, hummus, pickle spears, and lemonade.