Preheat the oven to broil. Split the French loaf in half, lengthwise, being careful to not slice all the way through. Drizzle the inside of the loaf with olive oil and toast under the broiler for 1-2 minutes until lightly toasted inside.
Spread the prepared mayonnaise on the bottom of the French loaf. Top with the cheese slices, alternating colors/flavors if using a variety. Layer on slices of turkey and bacon pieces.
Begin to fill in the sandwich with greens on top of the turkey. Start with the iceberg lettuce then fill in any gaps with other leafy greens. If using varying shades/flavors of leafy greens, be sure to have a visual mix of varieties across the entire loaf of bread. Season the greens layer liberally with fine sea salt and freshly cracked black pepper.
Gently fold thin slices of tomato in half and tuck, skin side out, into the sandwich. This will ensure any seeds or liquid from the inside of the tomatoes sops up into the bread and doesn’t drip down the outside of the sandwich.
Repeat the process of folding and tucking with the thin slices of red onion. Tucking and layering in- between the tomato and leafy greens.
Fill in any gaps with thinly sliced roasted red bell peppers and pickled jalapenos.
Finally, spread pesto inside across the top of the toasted French loaf.
Serve on a platter as one big sandwich for a crowd or slice into individual sandwiches right before serving.