Get pins with a glass or hard plastic head. The cheap pins with the soft plastic heads have a distressing habit of punching through the head and into your finger when they encounter resistance more solid than cloth. Tool for applying spackling paste. A fast-food plastic knife is adequate. Medium artist's bristle paintbrush .
Similar houses exist in primitive areas all over the world, especially in the tropics.
The same techniques are used for larger structures. All sizes given are for use with 25mm figures. Reduce or enlarge accordingly for other sizes. Cut a piece of foamcore long enough to allow you to lay out all 4 walls in a line. Draw out the four walls lightly with a sharp pencil, full width and touching.