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.
Bala
Bala is a market town and area in Gwynedd, Wales. Previously an urban area, Bala lies within the historical county of Merionethshire. It exists at the north end of Llyn Tegid, 17 miles (27 km) north-east of Dolgellau, with a population taken in the United Kingdom Census 2011 of 1,974. It is little greater than one wide street, this being Stryd Fawr (High Street, literally "Great Street"). The High Street and also its shops can be fairly active in the summertime with lots of vacationers. Bala was placed as having the 20th highest percent of Welsh language speakers in Wales by selecting division, in the United Kingdom Census 2011. According to the census, 78.5% of Bala's population can talk Welsh.