Season the pounded chicken breasts with kosher salt and freshly ground black pepper. Place them in the skillet and cook for about 7 minutes on each side until fully cooked.
Remove the chicken from the skillet and let it rest for a few minutes before slicing.
Lay two bread slices with the mayo side facing up, and layer one slice of Swiss cheese, two slices of ham, and a sliced piece of chicken on top of each.