Top Ciabatta: Spread pesto and layer with half the turkey slices.
Bottom Ciabatta: Spread mayo, layer 4 tomato slices, salt&pepper, and sprinkle the shallot. Cut a single slice of cheese into 4 quarters. Then, layer the cheese so each ciabatta bottom has 2.5 slices (2 + 2 quarters), making the bread fully covered.
Bake until cheese has melted, then broil for a few minutes until the cheese is nicely browned.
Assemble top on bottom, and eat right away.