From Mike's own summary in the comments section of Part 3:
Buy some 1/4" x 3/8" stripwood & use graph paper for your template ... Make a frame for each section ... I space them about 2" apart & also 3" spaces for doors & 2-1/2" for windows or whatever opening you want. I glue a horizontal piece 7" high & another under the windows. And the top & bottom plates (studs) equal the wall lengths.
You'll need matboard to glue on each side of all the frames. I glue the frame on a full sheet of matboard - squaring it into the top left hand corner. Put some weight on it & let it dry, then trim the right & bottom edge, & all the openings. Then flip the frame over & glue it to another sheet of matboard. Put some weight on it & let it dry, then trim the right & bottom edge, & all the openings.
Dry fit, decorate, add doors & windows etc.
Nail, screw, dowel or just clamp & glue all the parts together.