Decide where you want your openings for dollhouse scale windows and your door. The porch joins the wall ¾ of an inch above the base of the wall you have cut out, so make sure you draw a line ¾ of an inch above the base of the wall and measure the height of your window and door placement above that!
If you plan to use board and batten siding as a finish, remember that battens (covering joins in the siding) usually line up with the edges of windows and doors, and that spacing between battens should be fairly similar to accurately resemble siding. Check the finished facade example to see how the lines run along windows and doors.
When you have decided on the position of your door and windows, use a power jug saw if possible to cut out the openings. Drill a starting hole in one corner, then begin your cut with the power jig saw from that point.
If it is not possible to use a power jig saw, use a sharp utility knife held firmly against a steel ruler and score the cutting line several times before pressing down for the cut through the Gatorfoam board surface.