In a small bowl, stir together the mayonnaise with the mustard. Toss the herb salad mix in a separate small bowl with the extra-virgin olive oil, lemon juice and some salt and pepper.
Slather both cut sides of the bread with the mayonnaise-mustard mixture. On one slice of bread, layer on the meatloaf slices, pickles and then the salad. Top with the second slice of bread, slice and serve.