Under excitation with an external electromagnetic field, gold nanocones act as efficient optical antennas. In this work, a process developed for the fabrication of sharp-tipped gold nanocones on silicon is extended to transparent substrates covered by a thin conducting layer. In this configuration, the cones can be investigated in scanning probe microscopes while illuminating from below. The electric coupling between cones and substrate and between individual cones can be varied by a precise thinning of the conducting layer via a fine-tuning of the original layer thicknesses.