Lay the dollhouse on it's back in order to install the porch roof panels.
I will paint mines later, when the glue is dry because there is good accessibility all around for me to do so after installation.
Use a rubber mallet to get tabs into the wall slots.
Run glue all along the joints after installation and make sure all joints line up and are square to each other where the panels meet.
Clamp with masking tape and let dry.
