Place oven racks in upper and lower thirds of oven; preheat to 200°. Working in several batches, cook cabbage leaves in a large pot of boiling salted water just until translucent and bright green, about 2 minutes per batch. Using a large slotted spoon, immediately transfer leaves to a large bowl of ice water; let cool. Drain cabbage leaves well and dry thoroughly.
Set a wire rack inside each of 2 large rimmed baking sheets. Arrange cabbage leaves on racks in a single layer. Bake until completely dry and crisp, about 3 hours. Season with salt.