Heat oil in a nonstick frying pan over medium heat. Add crabcakes to pan and cook, turning once, until golden and warmed, about 5 minutes total. Meanwhile, whisk together mayonnaise, pickles, and pepper in a small bowl to combine.
Cut focaccia into 4 squares big enough to fit 1 crabcake per square and split each horizontally; toast bread.
Toss dill and lettuce in a small bowl to combine. Spread inside of focaccia tops with pickle mayonnaise. Set focaccia bottoms on plates and top with crabcakes, dill-lettuce salad, and onion, then focaccia tops.
*We especially love Portland-based Picklopolis's naturally fermented garlic dill pickles (picklopolis.com).
Note: Nutritional analysis is per burger.