||Preheat oven to 400. Remove skin from salmon fillets. Season both sides with salt, pepper, thyme and rosemary. Slice potatoes, with skins on, into rounds 1/8 inch thick. Toss potato slices with olive oil, salt, pepper, thyme and rosemary.
On a baking sheet, arrange overlapping potato slices in rectangles slightly larger than salmon filets. Roast potatoes for 8 minutes, till lightly browned and cooked through (test a small slice).
Meanwhile, cook garlic in olive oil, then at spinach and sauté over low heat. At the same time, toast pine nuts in a small pan. When spinach is cooked, stir in pine nuts and season with salt, pepper and lemon juice.
Place salmon filets, skinned side down, on the potato piles and lower oven temperature to 375. Cook till salmon is just cooked through, about 8 minutes depending on thickness of filet.
While salmon is cooking, portion spinach onto plates. Slide stacked potatoes and salmon on top of spinach. Garnish with a lemon slice.