Peel and thinly slice the bananas. Place them in a bowl and gently toss with the lemon juice. Add the coconut oil mixture and toss to coat evenly. Place in a single layer on the prepared baking sheet. Bake for 10-12 minutes, remove from the oven, and with a fork carefully turn each banana slice. Bake for an additional 10-15 minutes, until they are golden to medium brown.