Preheat the oven to 400 degrees F. Line a baking sheet with parchment paper.
In a mixing bowl, combine the ground beef, breadcrumbs, egg, garlic powder, salt, and black pepper. Mix until the ingredients are evenly distributed.
Form the mixture into 8 meatballs of equal size and place them on the prepared baking sheet.
Bake the meatballs for 18 minutes until they are cooked through.
While the meatballs bake, warm the marinara sauce in a small skillet over low heat.
Remove the meatballs from the oven. Place one mozzarella round on each meatball and return the sheet to the oven for 2 minutes until the cheese softens.
Press one olive half, cut side down, into the center of each mozzarella round to form the eyeball.
Spread a spoonful of marinara sauce on the bottom half of each slider bun. Set one meatball on the sauce and add the top bun.