Line a baking sheet or large plate with parchment paper. To the sheet, arrange 20 cookies in rows, flat side up.
Measure out 1 teaspoon sized pieces of filling, roll into balls, and place over each cookie. Add another cookie over each one, gently pressing down to make a sandwich, making sure you don’t press so much that the filling oozes out the sides. Transfer the baking sheet to the freezer for 30 minutes, just until the filling sets. This ensures the pb won’t melt when you coat them in chocolate. Remove from freezer after 30 minutes.
In a medium, microwave safe bowl, add the chocolate chips and the coconut oil. Microwave in 30-second increments until the chocolate is smooth and shiny.
Working one at a time, gently drop the sandwich cookie into the chocolate, using a small spoon to coat the top with chocolate. Using a fork, lift the cookie out of the chocolate, allowing excess chocolate to drip off before adding back to the parchment paper-lined baking sheet. Repeat with the remaining cookies.
Sprinkle with flaky salt (or wait until the chocolate has hardened a few minutes in the freezer to do so). Transfer back to the freezer for 30 minutes, or until the chocolate coating has set.
Remove and transfer finished cookies to an airtight container. Store in the fridge or freezer.