See the different ways a proper base can be done for a garden log cabin.. http://www.southwicks.co.uk/gallery-garden-office2.html
Concrete paving slab base - 16' x 10'
(Materials: 2 tonnes compressed scalpings, 1 tonne grit, 150 kg cement)
Railway sleeper base on compressed scalpings - 12' x 8'
The all in one home office – The Ruminator. Combining a unique and striking design with fantastic all round build quality.The attractive appearance blends well into your garden. Security is given high priority as is insulation. The Ruminator creates a beautiful outdoor office or garden retreat.