Season the chicken with salt, pepper, and your favorite herbs. Let it sit at room temperature for 10 minutes. Cook the bacon in a skillet until crispy, then set aside on paper towels, reserving some fat to cook the chicken.
Use the reserved bacon fat to cook the chicken until golden and fully cooked (165°F internal temp). Let it rest for 5 minutes before slicing to keep it juicy and tender.
Combine mayonnaise with minced garlic and fresh herbs in a bowl. Add a pinch of salt and pepper, tasting to adjust the flavors. This spread adds creaminess and a fresh, aromatic note to the sandwich.
Toast sourdough slices until golden brown using a toaster, grill pan, or broiler. Crispy bread creates a perfect contrast to the soft chicken and fresh veggies.
Spread herb mayo on each bread slice. Layer lettuce, tomato slices, sliced chicken, and crispy bacon on the bottom slice. Top with the second slice and serve immediately while warm.