Heat 2 teaspoons olive oil in a large skillet over medium. Add the kale, stir to coat, then cook, stirring occasionally, until the kale begins to soften, about 5 minutes. Add the garlic, 1/8 teaspoon salt, 1/8 teaspoon pepper, and red pepper flakes. Stir and cook 1 additional minute. Remove from heat, stir in the feta cheese, then cover to keep warm.
Toast bread in a toaster, toaster oven, or beneath a broiler. Set aside.