Spray 2 (8-inch to 10-inch) cake pans with nonstick cooking spray and preheat the oven as the cake mix box directs.

Prepare the cake mix is the label directs, replacing the water with whole milk and the oil with melted butter. Add 1 more egg than the label directs. Add the vanilla and salt; mix until smooth.

Divide the batter among the prepared pans. Bake as the label directs. Let cool in the pan 2 to 3 minutes, then run a knife along the outside of the cake pans and invert onto a cooling rack to cool completely.

Place 1 cake on a plate or cake stand; top with some frosting. Add the remaining cake and press down gently. Cover the entire cake with a thin layer of frosting. Refrigerate until firm, this is your crumb coat (or rough coat) of frosting. Cover with another layer of frosting until smooth.

Dye some frosting different colors using food coloring. Divide among piping bags fitted with a small round tip. Use the frosting to write your saying and decorate in a cross-stitch pattern by making a pattern with X shapes.