In a large mixing bowl, fully incorporate the oats and rice cereal.
In a medium saucepan over medium heat, add the oil, corn syrup, vanilla, and brown sugar.
Stirring constantly, bring to a boil. Let boil for 45 seconds and then remove from heat.
Add the peanut butter and stir until smooth.
Pour the peanut butter mixture over the oats and rice cereal and begin to work it with a spatula until oats and cereal are fully coated.
Place a piece of parchment paper on a medium-sized cookie sheet and pour the mixture on top of the prepared baking pan. Spread to mostly cover the whole cookie sheet.
Place another sheet of parchment paper over the mixture and using a rolling pin, flatten the mixture to cover the whole sheet and form into an even layer. Sprinkle with the peanut butter chips and a little bit of flaky sea salt (if using).
Let cool for 1 hour then remove from sheet and cut into bars.