Answer:
Increase the total area of direct contact between the two materials and decrease minute deviations from direct contact of the materials, also use a superconductor as a "mortar." Additionally ensure the two materials are of different conductivity. Additional mass may be used to add to the gravitational force pressing down on the surfaces once they make contact. Additional friction can be achieved by the use of force on the lower surface only, allowing the upper surface to remain static.
Apply glue or tar to the surfaces in contact.