Peel and core the apples, you should end up with about 1.5 pounds of apples.
Dice into 3/4-inch pieces.
Add all the ingredients except for the cornstarch to your Instant Pot. Mix.
Close and lock the lid. Turn the vent on the lid to the sealing position.
Press Manual or Pressure Cooker button (depending on your model) and using the arrow buttons set the cook time to 2 minutes. Use default High Pressure.Depending on your Instant Pot model and how cold the ingredients are, it'll take around 6-8 minutes to come to pressure.
Once the Instant Pot beeps that 2 minutes of cooking are done, do a Quick Pressure Release. This will take about 1-2 minutes.
Add 4-5 teaspoons of liquid from Instant Pot to a small bowl with cornstarch. Mix really well until all the cornstarch dissolves. Make sure to scrape all the cornstarch off the spoon also as it'll become pasty there.
Add the cornstarch slurry back to Instant Pot, scraping all of it from the bowl.
Press cancel on Instant Pot to stop Keep Warm function from working. Press Sauté button.
Mix the apple pie filling to evenly distribute the cornstarch slurry and cook on sauté for about 2-3 minutes until the mixture thickens.
Increase cooking time to 3 minutes for softer apples.
Use 1-2 extra teaspoons of cornstarch for thicker apple pie filling if desired.