• Preheat the oven to 350°F. Line large baking sheet with parchment paper and set aside.
• Add the box mix, eggs and vegetable oil or melted butter to large mixing bowl. Use a hand mixer to mix the ingredients together on medium speed until everything is fully incorporated.
• Use a 1-inch cookie scoop with release handle to scoop individual portions of dough onto the prepared cookie sheet. Repeat until all dough has been portioned into individual cookies, leaving approximately 2 inches between each scoop to allow for spreading.
• Bake the cookies 7 to 10 minutes or until edges are just lightly golden.
• Allow cookies to cool on the baking sheet for 5 minutes, then transfer them to a wire cooling rack. Allow them to cool completely before glazing.

Glaze

• Once cookies have cooled completely, sift the powdered sugar into medium bowl. Whisk in the lemon juice and the milk until you've got a smooth glaze. If the glaze is too thick, whisk in additional splash of milk. If it's too thin, add a little more powdered sugar.
• Spoon or drizzle the glaze over tops of the cooled cookies.
• While the glaze is still wet, sprinkle lemon zest over the top, or lay a lemon slice on top of each cookie. Then, leave the glaze to set before serving or storing.