Yes, your shed does need a base. This is to give it a solid, level foundation. Open soil will not help with the longevity of the shed itself or the contents within. The best materials to use to make your shed base are concrete, natural stone or wood.
Heriot
Heriot is a small village in the Moorfoot Hills southeast of Edinburgh, Scotland, within Eildon (part of the Scottish Boundaries council location, though traditionally in Midlothian). The village makes up some 150 residences, spread over a geographical area of around 50 square miles (130 km2), most of which is moorland. Linked to the rest of the globe largely through the A7 road, Heriot had a train station from 1849 up until the branch line closures initiated by Beeching created the track to be boosted in the 1960s. The Scottish Parliament voted, in 2006, to reinstate the railway, but without a station at Heriot. The School (as of Sept 2016) has 36 pupils. There are numerous community groups running in the town including dramatization teams, WRI, an area choir and a karate club. Places close to Heriot include Borthwick, Carcant, Crichton, Fala, Stow of Wedale and also Innerleithen.