Place the rooms, draw the circulation; the fit and the critic follow.
Drag rooms (edges change the proportion, Alt the size; edges snap to walls nearby, Ctrl to place freely) and fixtures; pull the arrow on a room's edge out for a leg (an L); click a line to select it, drag its points; Delete removes it. V select, L line, E entrance, X exit, F fixture, W window. A short line from inside one room into another is a door.
One LP: no overlaps, inside the plot, a door's wall for every way in, rooms held to their facade, the circulation as read.