Cake layers must be completely cool to the touch; for best results, freeze the cake layers for about 15 to 30 minutes.
Slice the red cake and the white (uncolored cake) horizontally into 2 layers. You should end up with 2 layers of red and 2 layers of white.
Using a cake board or a flat dish, stack one of the white layers on the bottom and spread a thin layer of frosting on top.
Add a red layer of cake on top of the white layer and spread a thin layer of frosting on top.
To assemble the top half of the cake, place a white layer of cake on a piece of parchment paper or aluminum foil and top it with a red layer and the blue cake. You should have a stack of white, red, and blue (bottom to top).
Using a 4 or 5 inch circle as a guide (I used the lid to a quart sized plastic contained), cut a circle in the center of the 3 cake layers. Use a butter knife and be sure to cut all the way through the layers.
Gently lift the circle out and separate it from the surrounding circle.
Take the outer layer of the blue cake and the inner layer of the red and white layers (you will NOT need the inner blue circle or the outer red and white layers - use for cake pops or snacking).
Place the blue outer circle on top of the frosted red layer and spread a thin layer of frosting on the inside of the blue circle.
Fit the red and white smaller circle layers inside the blue layer.
Using the remaining frosting, apply a thin layer of frosting to crumb coat the cake and let set in the refrigerator for an hour or so.
Frost the rest of the cake and decorate as desired. I have make plain or also with red and blue sprinkles.
For best results, let the cake set overnight after decorating