Combine 2 cups cold water, wine, onion, carrot, celery, lemon juice, salt, pepper and thyme in slow cooker. Cover and cook on high for 20 minutes.
Carefully lower salmon fillets into liquid. Pour in additional warm water, if needed, so that liquid just covers salmon. Cover, reduce heat to low; cook until salmon is light pink and firm, 35 to 40 minutes. Gently lift out and serve warm, or let cool, wrap in plastic and refrigerate.