Shred fish with your fingers. Combine salmon, garlic oil, and salt. Fit into a ring mold on serving plate and reserve in refrigerator.
Mix watercress, oil, lemon juice, vinegar, garlic, and salt in a food processor until pureed, but slightly chunky. Spoon this sauce around the edge of the ring mold with salmon. Carefully remove the mold. Top with seasonal garnishes; if desired, serve with seeded crackers.