You could choose a concrete base, a timber base, or paving slabs for your shed, but there are steps you should take regardless of what you choose. This starts with preparation before building begins.
Prepare the ground
Ground preparation will help to create a stable shed. Clear the area, measure and mark to make sure the base matches the shed, and level the ground within the marked area. Compact the soil and think about water drainage and the possibility of collecting and reusing water. Check that the ground is level and use a weed membrane if required.
Base materials
What you do next will depend on what base material you choose. If you go for concrete Cheltenham, supplied by companies such as //www.monstermixconcrete.co.uk/concrete-cheltenham/, start by building a pressure-treated wood formwork to contain your concrete mixture. Aim for a 15cm base height, made up of a 7.5cm layer of compacted hardcore covered with sand. Use 5 parts ballast to one part cement for the best results or go for dry-mixed concrete bags and add water.
If you opt for paving slabs, work row by row from a corner. Stand slabs on their edge and then tip into your gap.
Timber bases are another option and base frames can simply be secured with ground spikes. Use a spirit level to ensure evenness. This is important with all shed bases to ensure stable results. Check all points that floor bearers will touch and add extra material for support to prevent shed damage.