I am glad you soil is clean Andrew, as in ‘solarisation’.
There is no specific method, it depends on your resources. I make a small hole with my trowel so tubers are just buried, then pull a little surface soil up to make a small hill, and cover that with three to four inches of compost or manure, which carries on enriching the soil after potato harvest, which is by just pulling up the main stems.
You probably can plant now in Spain, if moisture is available, but here it is harvest time with blight and slugs imminent, if not present already on leaves and in tubers respectively.