In a medium-sized bowl, combine the peanut butter, honey, vanilla, and salt. Microwave for 20-30 seconds and stir until combined.In that same bowl, add in the rice krispie cereal, flaxseed, and oats. Stir together until completely combined.Add in the optional add-ins if desired.Place in the fridge for 20-30 minutes for easier forming.Form balls with the mixture and then flatten the balls in your hand to create a cookie shape.If desired, melt 3 tbsp. of milk chocolate chips in the microwave. Put the melted chocolate in a small Ziploc bag and cut a small hole in the tip of the bag. Drizzle the chocolate across the cookies and let the chocolate harden.Store cookies in an airtight container for 4-5 days or freeze for up to 3 months.