Heat the olive oil in a large skillet over medium-high heat. Add the garlic and cook, stirring frequently, until fragrant, about 1 minute. Add the spinach a large handful at a time, stirring constantly between each handful, until slightly wilted and more spinach can fit in the skillet. Cook until the spinach is completely wilted but still a vibrant green, about 5 minutes. Stir in the sambal oelek, 1 teaspoon salt and a few grinds of black pepper. Transfer to a serving platter or bowl.