1. Slice lobster meat from tail and claws crosswise pieces, about 3/4-inch thick. Spread the mayonnaise on the brioche slices, and place them in a row on your work surface. Arrange half the quantity of tomato, field greens, bacon, and lobster meat between two slices of brioche.
2. To assemble, stack the second layer on top of the first layer with ingredients facing up. Place the last piece of brioche, mayonnaise-side down, on top of the second layer. Pierce opposite corners of the sandwichÂ’s top layer with lobster picks or decorative toothpicks. Slice the sandwich on the diagonal with a serrated knife.