Combine first 10 ingredients in a fish poacher.* Bring to a boil. Cover, reduce heat, and simmer 30 minutes. Cool to room temperature; strain reserving liquid. Discard solids. Return liquid to poacher.
Remove the head, tail, and fins from salmon. Wrap fish in cheesecloth; tie ends with string. Place fish in poaching liquid; add water to cover by 1 to 1 1/2 inches. Cover and bring to a simmer; simmer 20 minutes. Remove from heat, leaving fish in liquid for 15 minutes. Remove fish from liquid. Cool. Cover and refrigerate for 8 hours.
Remove cheesecloth. Remove and discard skin. Place fish on a platter, and garnish with cucumber slices, lemon slices, and fresh dill. Serve with Cucumber-Dill Sauce, Watercress Sauce, and Aïoli.
*A large oval roasting pan may be used.