Cook the ground beef in a skillet over medium-high heat. Season with salt and pepper. Break the beef into small chunks.
Add the marinara sauce to the beef. Stir.
Add the egg, ricotta, remaining spinach, and Parmesan reggiano to a bowl. Stir to combine the ingredients.
Layer the baking pan with marinara followed by the ricotta mixture. (I started with using the sauce to coat the pan because I feared the noodles on the bottom would not soften up without sauce on the bottom to coat.)
Break the lasagna noodles into smaller pieces to fit the pan. Add the noodles to the pan.
Add marinara and the ricotta mixture. Add mozzarella cheese.
Continue to create layers with the noodles, marinara, ricotta mixture, and mozzarella.
When you reach the final layer, sprinkle the cheddar cheese over the top.
Cover the top of the pan with foil to prevent water from getting into the lasagna.
Add a 1.5 cups of water to the pot. Place the trivet inside the pot. (This comes with the device).
Create a foil handle to remove the pan from the Instant Pot. Fold a large piece of foil in half the long way. This will be used to wrap around the pan to make it easier to lift out of the Instant Pot.
Place the foil handle in the Instant Pot. Place the pan in the middle of the pot over the foil handle.
Set the Instant Pot on manual, 20 minutes. After the Instant Pot alerts that 20 minutes have passed, allow the steam to settle without quick release for 10 minutes.
Unfold the foil handle and remove it from the Instant Pot. Place the pan on a baking rack to cool. Allow it to cool to room temperature.
I used a jar of peanut butter to assist with removing the lasagna from the baking pan. I placed the pan on top of the jar and then pressed down on the sides of the pan to remove.