Line an 8×8-inch pan with parchment paper, leaving an overhang on two sides to lift the slab out later. Lightly oil the parchment if you prefer easier release.
Combine the nut butter, honey, and butter (or coconut oil) in a small saucepan set over low heat. Warm gently, stirring constantly, until the mixture is glossy and smooth — about 2 to 3 minutes. Remove from heat and stir in the vanilla.
In a large bowl, whisk together the oats, flaked coconut, protein powder (if using) and the measured 1/8 tsp sea salt so the dry items are evenly distributed.
Pour the warm nut-butter mixture over the oat mixture. Use a sturdy spatula or wooden spoon to fold and press the wet ingredients into the oats until every bit is coated and the mixture holds together when squeezed.
Fold in half of the chocolate chips so they are mixed through. Transfer the mixture to the prepared pan and press it very firmly into an even layer — use the bottom of a measuring cup or a piece of parchment to compact it tightly.
Scatter the remaining chocolate chips on top. For a neat finish, press them lightly into the surface. Sprinkle a small pinch of flaky sea salt across the top to boost flavor.
Chill the pan in the freezer for 15 minutes to set quickly, then move it to the refrigerator for another 30 minutes until firm. This two-step chilling firms the bars evenly and helps slicing cleanly.
Lift the chilled slab from the pan using the parchment overhang and place it on a cutting board. Trim any uneven edges and slice into 18 bars (3 rows by 6 columns) or your preferred size. Store bars in an airtight container in the fridge for up to 10 days or freeze for longer storage.