First, roast the walnuts. Preheat your oven to 350 degrees. Note: You can also make these without roasting them, but roasted walnuts are a little crunchier and have a deeper nutty flavor.
Line a sheet pan with parchment paper and arrange walnuts in a single layer.
Roast for about 7-8 minutes until walnuts are fragrant. Allow to cool for 15-20 minutes and then transfer to a bowl. Save your sheet pan and parchment paper, you'll need both for next steps (add new parchment paper if needed).
Add dark chocolate to a microwave-safe bowl. Microwave chocolate in 15-30 second increments until smooth and creamy, stirring with a spoon in between microwave sessions.
In small batches, add walnuts to the bowl of melted chocolate and toss gently with a fork until the walnut is coated to your preference (you can coat each walnut completely, do them in clusters or leave them partially uncoated).
Remove the walnuts from the bowl by lifting with the fork and allowing excess chocolate to drip off.
Place chocolate coated walnuts on the parchment paper lined sheet pan in an even single layer.
Finish by sprinkling with flaky sea salt. When finished, put the sheet pan in the freezer for 5 minutes to set the chocolate.
Transfer to an airtight container and store in the fridge for up to 2 weeks.
Notes
Note: You may need to adjust the amount of chocolate chips based on how thickly or thinly coated you like your walnuts.