Preheat oven to 400°. Bake them at a high temperature for about 20 minutes instead of baking them at a lower temperature for a longer period. A long, low bake (say 375°F or below) will result in tender sweet potatoes, but never crisp.

Don’t overcrowd the baking sheet. Spread the sweet potato slices into a single, even layer, leaving space around each slice. When too many ingredients are on one baking sheet, the heat from the sheet gets trapped under the food and creates steam, and the sweet potato slices will be tender instead of crisp.

Let the sweet potato chips cool on a cooling rack for about 10 minutes after you take them out of the oven.