Melt the chocolate chips and coconut oil together over a double boiler. Line a baking sheet with parchment paper or wax paper.
Slice the apple into 1/4-inch-thick slices. Dip the apple slices one at a time into the chocolate, making sure to coat them evenly. The chocolate should go at least three-quarters of the way up each apple slice. Let the excess chocolate drip off.
Press one side of each slice into the peanuts or coconut, and place the slices non-peanut/coconut-side down on the parchment. Place in the fridge or freezer until the chocolate hardens, 10 to 15 minutes. Serve.