Cook bacon to crispy but not brittle: pan-fry over medium heat 2–4 minutes per side or bake at 400°F (200°C) on a rimmed sheet for 12–18 minutes depending on thickness. Transfer to a paper towel-lined plate to drain and keep warm.

Prepare avocado (optional)

If using avocado, scoop half of a ripe avocado into a small bowl. Add 1 tsp lemon juice and a pinch (about 1/8 tsp) of salt. Mash lightly with a fork so it remains slightly chunky. Set aside.

Make spread

In a small bowl combine mayonnaise (2 tbs), Dijon mustard (1 tsp), olive oil (1 tsp), remaining lemon juice (if any), 1/8 tsp black pepper and 1/8 tsp salt. Whisk until smooth. Taste and adjust seasoning.

Prepare bread

Slice ciabatta rolls or sourdough horizontally. Spread softened butter thinly on the cut sides. In a skillet over medium heat, toast buttered sides until golden (about 1–2 minutes) or toast under broiler for 1–2 minutes, watching closely so they don’t burn.

Assemble sandwich

Spread about half of the mayonnaise-mustard mixture on the bottom half of each roll and the rest on the top half. Layer on each bottom half: 3 oz (half) sliced roasted turkey (arrange evenly), 1 slice Swiss cheese, 1 cooked bacon strip (break in half if needed), 1–2 tomato slices, 1 leaf red lettuce, 2 red onion rings, 2 pickle slices, and mashed avocado if using. Top with the remaining turkey (to reach total 6 oz), remaining bacon strip, second Swiss slice, and the top half of the roll.

Melt cheese (optional)

If you prefer melted Swiss, after assembling place the open-faced bottom halves (cheese on top) under a broiler for 30–60 seconds until cheese softens and just melts. Then finish stacking with top half.

Finish and serve

Press sandwich gently to compact, cut in half on a diagonal, and secure with toothpicks if desired. Serve immediately with extra pickles or chips.