Season the chicken with the cumin, oregano, paprika, and salt. Stir together the mayonnaise and adobo sauce. Set both aside.
Cook the bacon in a grill pan or panini press on medium heat, turning once, until crisp, 4 to 6 minutes. Drain it on paper towels.
Discard the fat from the pan. Cook the chicken in the pan until browned and no longer pink in the center (165°F internal temperature), 3 to 4 minutes per side. Remove it to a cutting board.
Spread the mayonnaise mixture over the bread. Arrange the chicken, tomato, lettuce, bacon, and avocado over four of the bread slices, mashing the avocado slightly. Add the remaining bread slices, compressing the sandwiches.
Cook the sandwiches in the pan under a heavy weight (such as a heavy skillet) until they are browned, 3 to 4 minutes per side.
Tip: A slice of center-cut pork bacon contains only 60 calories, 1.5 grams of saturated fat, and 260 milligrams of sodium. It can be a healthier choice than turkey bacon because some brands add loads of sodium.