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.
Perranporth
Perranporth is a seaside hotel town on the north shore of Cornwall, England, United Kingdom. It is 1 mile east of the St Agnes Heritage Coastline, and around 8 miles south-west of Newquay. Perranporth and its 3 miles (5 km) long coastline encounter the Atlantic Ocean. It has a population of 3,066, as well as is the largest settlement in the civil parish of Perranzabuloe. It has a selecting ward in its own name, whose population was 4,270 in the 2011 census. The town's contemporary name comes from Porth Peran, the Cornish for the cove of Saint Piran, the patron saint of Cornwall. He started St Piran's Oratory on Penhale Sands near Perranporth in the 7th century. Hidden under sand for several centuries, it was discovered in the 19th century.