A novel scalable procedure for the thermally initiated polymerisation of bonded monolithic porous layers of controlled thickness within open tubular fused silica capillaries (monoPLOT columns) is presented. The technique further uses an in-process measurement of the polymer stationary phase growth using capacitively coupled contactless conductivity detection (C4D).Porous polymer layers of polystyrene-divinylbenzene and butyl methacrylate-ethylene dimethacrylate of variable thickness and morphology were fabricated inside fused silica capillaries using combined thermal initiation and laminar flow of the polymerisation mixture. The procedure enables the production through thermal initiation of monoPLOT columns of varying length, internal diameter, user defined morphology and layer thickness for potential use in both liquid and gas chromatography. The morphology and thickness of the bonded polymer layer on the capillary wall is strongly dependent upon the laminar flow properties of the polymerisation mixture and the changing shear stress within the fluid across the inner diameter of the open capillary. Due to the highly controlled rate of polymerisation and its dependence on fluid shear stress at the capillary wall, the procedure was demonstrably scalable, as illustrated by the polymerisation of identical layers within different capillary diameters.Furthermore, the relationship between effective capillary diameter and C4D response was investigated for both types of polymers over a range of capillary diameters and layer thicknesses. Although in this case the in-process measurement technique was used during thermal initiation, it may also be applied to photo-initiated approaches for monoPLOT fabrication. This method provides an accurate, real-time measurement of the porous layer growth within the capillary, vastly improving column-to-column reproducibility. The technique was shown to be very precise, with a measured %RSD < 10%.