Solid wood flooring is most commonly installed by nailing it into a wooden subfloor, such as floorboards or plywood. However, it should not be nailed into chipboard, as it lacks the strength to hold the nails securely. The subfloor must be level, clean, and in good condition. If it's uneven or weak, it's best to first install a layer of ½-inch plywood to provide a stable base. This method ensures a secure, long-lasting installation for your solid wood floors.