I followed the tutorial at The China Doll with a few modifications.  Since the Newport is already brick, I opted for a stone foundation.  I cut my stones using different measurements from the ones used in the tutorial - 5/16" x 13/16".  I originally tried mimicking concrete blocks by doing a direct 1:12 scale conversion of the real thing, but the blocks looked too big in proportion.

The overall foundation with the two-story addition and the extended porch was a lot of surface to cover, but I lucked out with a chance sighting on freecycle of 20 cardboard egg cartons only 15 minutes from my house!  Again, the price was right, and there's a sense of accomplishment recycling something in a creative way.  I like a lot of the pre-made items available to finish dollhouse foundations, but I prefer making things myself.  It adds a more creative touch and is much less expensive.  Besides, most of the foundation will be obscured by the eventual landscaping.

I painted the foundation medium grey before gluing on the stone pieces.  Instead of breaking the pieces at the corners, I bent the pieces to follow the contour of the foundation.

I did use a spacer, but since the stones varied slightly in size there was no way to eliminate all irregular gaps.  The grout should make this less obvious.

I also cut the stones in half to finish the top edge for consistency, but the nosing along the first floor pretty much covers them up.

Once the glue dried, I used a stencil brush to dot on some white and medium grey paint mixed with glaze, blotting to keep the color application subtle.  I then sprayed the stones with two thin coats of matte sealer and let the foundation dry completely.

I applied the grout (Andi Mini Brick and Stone Mortar Mix) in its existing grey form with my fingers, wiping away the excess as I went along.  Doing small sections at a time, I pulled a round toothpick gently along the grout lines to enhance the realism of mortar between the stones.

I lost some of the darker tones with the application of the mortar, so I repeated the painting process I had done before the grout but with a much finer application of paint (more glaze than paint) and then applied one more thin coat of matte sealer spray.

click image to enlarge

I am glad I was able to do this process before the house was glued to the foundation; it made it much easier having the ability to flip the foundation in any direction I needed.