Line two sheet pans with parchment. Place the coating coconut in a shallow dish.
Add white chocolate chips and coconut oil to the slow cooker. Cover and heat on LOW for 45–60 minutes.
Stir until silky smooth. If needed, cover and warm 10 more minutes to fully melt.
Stir in vanilla and salt until combined.
Fold in chopped almonds and the 1/2 cup coconut. Let the mixture stand 5–10 minutes to thicken slightly.
Gently fold in mini marshmallows just to distribute.
Scoop heaping tablespoon mounds onto the pans. Roll each in coconut to coat all sides.
Chill until firm, about 20–30 minutes. Dust with powdered sugar if using and serve.