Prepare the pan: Line a 9x9 inch baking pan with parchment paper, leaving overhang on two sides for easy removal. Set aside.
Make the pretzel crust: In a medium bowl, combine 3 cups crushed pretzels, melted butter, and sugar. Mix until evenly moistened. Press firmly into the bottom of the prepared pan using the bottom of a measuring cup to compact evenly.
Prepare the caramel layer: In a microwave-safe bowl, combine unwrapped caramels and heavy cream. Microwave in 30-second intervals, stirring between each, until completely smooth and pourable (about 2-3 minutes total).
Assemble caramel layer: Pour warm caramel over the pretzel crust, tilting the pan to spread evenly. Let set at room temperature for 15 minutes until slightly firm to the touch.
Melt the chocolate: In a microwave-safe bowl, combine chocolate chips and coconut oil. Microwave in 30-second intervals, stirring frequently, until completely smooth (about 1-2 minutes total).
Add chocolate topping: Pour melted chocolate over the set caramel layer. Spread gently with an offset spatula to cover completely. Immediately sprinkle with flaky sea salt and optional crushed pretzels for garnish.
Chill and serve: Refrigerate for at least 2 hours, or until completely firm. Use parchment overhang to lift bars from pan. Cut into 16 squares using a sharp knife dipped in hot water, wiping between cuts. Store refrigerated.