You can glue the parts together using low temperature glue gun. Take care that glue is not too hot as it could melt some of the styrofoam.Next glue the bottom styrofoam plate which serves as base of the decoration frame.
Once that is done glue the corrugated cardboard to the edge of the back wall.
Begin at the base of decorations frame.Glue the cardboard in such way that smooth/flat side is facing outside and corrugated side is facing inside.
Glue only short length of cardboard at time, make sure that glue has cooled/dried and then continue to glue next short length of cardboard.
Continue this way until you have glued cardboard side wall to the whole edge of back wall.
Cardboard roll fits 100 % to all the shapes so this procedure is quite simple.
Once you get to the other side of the base cut the excess length of cardboard using scissors and glue the remaining length of cardboard to the edge of back wall.Once the decoration frame is completely assembled it can be filled with balloons of different size and colors. Balloons can be attached into the frame using double-sided adhesive tape or low temperature glue gun.There is patent pending for this decoration frame system.