Thinly slice sweet potato into ¹⁄₁₆-inch thick slices using a mandolin or sharp knife. Place slices in a large bowl. Drizzle with vinegar; toss to coat. Let stand for 20 minutes, stirring occasionally.

Place oven racks in the top third and bottom third oven oven. Preheat oven to 250°. Line two very large baking pans with foil. Generously spray with nonstick spray; set aside.

Drain sweet potato slices; pat dry with paper towels. Toss sweet potatoes in oil and salt in a medium bowl to coat. Arrange slices, in a single layer, in prepared baking pans. Bake for 1 hour or until lightly browned, turning slices over and switching baking pans on oven racks every 15 minutes. Turn off off. With oven door closed, let potato slices stand in oven for 2 to 3 hours or until desired crispiness. Serve immediately.