Preheat the oven to 225 degrees F (110 degrees C). Line a baking sheet with parchment paper.
Spread banana slices out onto the prepared baking sheet, making sure slices are not touching. Brush with lemon juice.
Bake in the preheated oven for 90 minutes. Check bananas, lifting slices up to separate from the paper once or twice. Continue baking until bananas are dried out, 30 to 90 minutes more.
Let bananas cool until crispy, at least 5 minutes.