Make crepe batter: In a blender, puree flour, sugar, salt, milk, eggs, and butter until smooth, about 30 seconds. Refrigerate for 30 minutes or up to 1 day; stir for a few seconds before using.
Prep pan and add batter: Heat an 8-inch nonstick skillet over medium. Lightly coat with butter. Quickly pour 1/4 cup batter into center of skillet, tilting and swirling pan until batter evenly coats bottom.
Cook crepe and flip: Cook until crepe is golden in places on bottom and edges begin to lift from pan, 1 to 1 1/2 minutes. Use an offset spatula to lift one edge of crepe, then use your fingers to gently flip crepe.
Finish cooking crepe: Cook crepe on second side until just set and golden in places on bottom, about 45 seconds. Slide crepe onto a paper towel-lined plate.
Repeat steps to cook more crepes: Repeat with remaining batter, coating pan with more butter as needed, and stacking crepes directly on top of one another. Let cool to room temperature before using.