Preheat oven to 400ºF and line a large baking sheet with parchment paper; set aside.
Combine milk and lemon juice in glass measuring cup or small bowl; set aside.
Make dough: In a large mixing bowl–or bowl of food processor–add flour, sugar, poppy seeds, baking powder, salt and lemon zest. Whisk until well combined and set aside–pulse dry ingredients together if using food processor. Using the S blade of the food processor, pulse the frozen coconut oil or vegan butter with the dry ingredients until broken down into small chunks. Or use grated butter method and work into dry ingredients with pastry blender.
Slowly add milk-lemon mixture, vanilla, and lemon extract until dough starts to form. The dough may seem dry, but continue working together with hands. If dough is sticky, use floured hands to shape for next step.
Shape dough into an 8″ circle on prepared baking sheet. Using a large, sharp knife, make 8 triangle slices into dough. Fully separate dough and space about 2" apart on baking sheet.
Bake for 15-20 minutes until edges and tops are lightly browned. Let scones cool on baking sheet for 5 minutes before transferring to wire rack to cool completely.
Make the glaze: While the scones are cooling, combine powdered sugar with lemon juice. Stir until no lumps are present. With scones on lined baking sheet, or cooling rack with baking sheet placed underneath, zigzag glaze over scones with knife or spoon. Sprinkle with more lemon zest if you'd like. Allow glaze to set, about five minutes, then enjoy!