We stacked them the way we would any tiered cake. We use a dowel on the bottom pillow (right in the middle) We’ve even used very large plastic straws when we didn’t have a real dowel. Then we put a small piece of cardboard which has been covered in foil in the middle of the bottom pillow. (See photo) Secure it with a touch of buttercream. Then lay the second pillow on top. Then we use a wooden skewer (because its pointy and tall) and put it through both layers. Use something (small hammer or in our case the back of an icecream scooper) to bang it gently through the cardboard pieces. Hope this helps you.
