Bring a medium pot of water to a boil; generously salt water and return to a boil. Prepare an ice-water bath; set aside. Place leeks in boiling water and cook until crisp-tender, about 1 minute. Drain and transfer to ice-water bath to cool. Drain, pat dry, and set aside. Repeat process with asparagus (cooking about 30 seconds), ramps (cooking about 1 minute), zucchini (cooking about 30 seconds), peas (cooking about 30 seconds), and fava beans (cooking about 1 minute). Peel fava beans and set aside.
In a medium bowl, mix together crab, mayonnaise, and olive oil. Divide crab mixture evenly between four chilled serving plates, spreading so that it is 1/4-inch high on the plate. Arrange leeks, asparagus, zucchini, peas, fava beans, and fennel on top of crab mixture; garnish with lily bulb petals, radishes, chile, and nasturtium buds. Drizzle with vinaigrette and sprinkle with sea salt; serve immediately.