Toast the sourdough bread slices until golden brown.
Spread mayonnaise on one side of each toasted bread slice.
Layer the bread with arugula, baby spinach, tomato slices, deli turkey, provolone cheese, cucumber, red onion, pepperoncini, and avocado.
Drizzle the layered ingredients with olive oil and sprinkle with salt, pepper, and oregano.
Place the remaining slices of bread on top, mayonnaise side down. Press gently to hold the sandwich together and slice in half.
To make the chia fresca, stir together the lemon juice and maple syrup (or honey) until well combined. Add the chia seeds and a pinch of salt. Slowly pour in the water while stirring gently to avoid clumping. Garnish with fresh mint.
Serve the sandwich with carrot sticks, hummus, and chia fresca.