Stir graham cracker crumbs and 2 tablespoons coconut oil together in a bowl. Press cracker mixture into the bottoms of the prepared muffin cups.
Combine chocolate chips and remaining coconut oil in a microwave-safe glass or ceramic bowl; melt in the microwave in 30-second intervals, stirring after each melting, for 1 to 1 1/2 minutes (depending on your microwave). Divide melted chocolate mixture evenly among muffin cups.
Press 1 marshmallow horizontally into chocolate in each muffin cup; refrigerate until chocolate is firm, 1 to 2 hours.
Set oven rack about 6 inches from the heat source and preheat the oven's broiler.
Bake s'mores in the preheated oven until marshmallows are browned and puffed, 1 to 1 1/2 minutes. Return muffin tin to refrigerator to set chocolate and marshmallow, 30 to 60 seconds. Loosen and remove s'mores from the muffin cups with a butter knife.
