The instructions tell you to assemble the foundation away from the dollhouse but I recommend you assemble it on the dollhouse itself. Assembling the foundation in this way, will guarantee that it fits squarely on the first floor of the dollhouse.
In order for your dollhouse to sit upside down, place it at the corner of your work table. That way the side walls hang off the edges of the table and do not interfere with this placement.
Assemble the foundation as the instructions recommend. You will not be able to install the front, long foundation piece yet. That will have to wait for the dollhouse to be turned right side up.
Use hand held weights to clamp the foundation down while the glue dries. Make sure you use masking tape to hold the weights in place, so they don't roll off and land on your foot, if the dollhouse is accidentally bumped.
While the dollhouse is upside down, run wood glue along the joints of the walls and ceilings. You will not be able to do this on the side of the floors, since they will be finished.
You can also use this opportunity to prime the ceilings and walls, once the glue is completely dry. That way your floors are protected from dripping paint.
