Abstract: An assemblage which forms in-situ monolithic concrete slab-on-grade foundations is an internally collocating monolithic forming unit, which unit is typically light weight enough to be maneuvered intact. The unit is comprised of a number of form members and an overhead screed. The concrete-surface-defining form members, preferably sections of light-gage cold-formed metal, also serve as struts defining foundation horizontal geometry by having controlled lengths and interconnections. Corresponding pairs of squaring wires control geometry as well, and are removed before finishing the concrete slab. Temporary support of the forming unit is upon coarsely threaded stakes. Each stake screws into earth with a high speed pneumatic impact wrench, and quickly secures simple form support components such as a slab clip.