Cream the peanut butter and butter. In a large mixing bowl or stand mixer with a paddle attachment, add the peanut butter and softened butter. Cream together on medium speed until smooth.
Add the powdered sugar, salt, and vanilla. On low speed, add the powdered sugar, salt, and vanilla extract. Continue to mix until combined, scraping down the bowl as needed.
Add the rice cereal. Stir in the crushed rice cereal until combined.
Shape and chill peanut butter balls. Line a large baking sheet with parchment paper. Scoop the mixture into tablespoon-sized balls (18-20 grams weighed on a food scale). Roll each ball between clean hands to shape and round the balls. If using natural peanut butter, the dough will be sticky and may not roll as well, so we roll them twice. Place the balls on the lined baking sheet and freeze for 15 minutes. Remove the balls from the freezer and roll once again to create perfect circular balls. Freeze for another 15 minutes (30 minutes total), until hardened.
Dip in chocolate. In a small microwave-safe bowl, combine the chocolate and refined coconut oil. Microwave in 30-second intervals, stirring between intervals, until the chocolate is smooth and glossy. Remove the peanut butter balls from the freezer. Using a fork, dip the balls in the melted chocolate, scraping any excess chocolate on the sides of the bowl. Drop the balls onto the lined baking sheet. Repeat until all the balls have been coated, then use a spoon to drizzle any leftover chocolate on top. Sprinkle with flaky sea salt, then place the tray back in the freezer for 20 minutes.
Chill to set. After 20 minutes, remove the tray from the freezer. Cut away any excess chocolate from the bottoms of the peanut butter balls and transfer the balls to an airtight container and into the refrigerator to continue to set. Refrigerate for up to 2 weeks.