Combine avocado, plain yogurt, tuna, and pickle relish together.

Place about 1/3 to 1/2 cup of mixture on top of one slice of bread. Top with 2 thin slices of cheese and another piece of bread.

Spread 1/2 Tbs of coconut oil on both sides of the sandwich.

Preheat skillet or grill to low-medium heat. Cook for about 2 to 3 minutes until sides are golden brown and cheese has melted.