First, preheat the oven to 350ºF and spray a baking sheet with nonstick cooking spray.
Next, combine melted butter and brown sugar until there are no lumps. Then, add maple syrup, egg, peanut butter, and vanilla and mix again.
Add salt, quick-cooking oats, rice crispies, and baking soda and mix until everything is combined. Add in the rice crispies, chocolate chips, and shredded coconut, and mix one more time.
Refrigerate dough for 20 minutes to set.
Scoop 1.5 tablespoons of batter into your hands and form it into a ball. Place it onto the cookie sheet and slightly press down to form a cookie shape. The batter will feel a bit sticky, but it will be so soft and chewy when done baking!*
Repeat the process above until you've fit 8-10 cookies on your baking sheet.
Bake cookies at 350ºF for 11-14 minutes or until they begin to turn golden brown on the bottom.
Remove cookies and let them cool for a couple of minutes on the baking sheet before transferring them to a wire rack. Sprinkle on some coarse sea salt and continue to let cool for at least 20 minutes to firm up.