Prepare the dressing by whisking together the ginger, sugar, lime juice, garlic and water. Refrigerate overnight.
Tightly layer together in a mold one fourth of each of the microgreens, tomatoes, cucumbers, mango, onions, avocado and crab. Use a hollowed out aluminum can if you don't have a mold.
Press down on the top layer while slowly removing the mold to reveal the crab stack. Repeat with the remaining ingredients to form a total of four crab stacks.
Drizzle the crab stacks with the dressing and serve.