Preheat the oven to 250F with the top rack positioned in the middle. Then, line two baking sheets with parchment paper.
In a shallow bowl or pie dish, combine ½ cup water with 2 tablespoons lemon juice.
Slice the bananas between ⅛ and ¼-inch slices. Soak them in the lemon water mixture and transfer them to the lined baking sheet, making sure there's a little space between each slice. They can be tight but in a single layer.You can also brush them with the lemon juice mixture using a basting brush.
Bake
Bake them in the preheated oven for 1 ½ to 2 hours or until they are mostly crispy, flipping them over halfway through and swapping the baking sheet positions about 1 hour in. Visually, they'll be medium golden brown, with some yellow left.
Remove the sheet pans from the oven and let the banana chips cool down completely on the counter. They'll be slightly soft at first, but they crisp up as they cool.
Storage:
Once the banana chips have fully cooled, transfer them into an airtight container or zip bag where they'll keep for a week at room temperature.
Notes
Make them sweet:Use ripe bananas and sprinkle with cinnamon after brushing with the lemon water. Follow the baking directions above.
Make them spicy: Add ¼ teaspoon of sriracha or hot sauce to the lemon water mixture and brush it over the banana slices.
In the air fryer: Slice the bananas evenly and cook them at a low temperature until lightly golden. At 250F they'll take about 35 minutes. At 300F they'll take about 25 minutes, although every air fryer cooks a little differently.