It is necessary to have a flat, hard level surface to set your Gazebo on. This is very important and key to how your Gazebo will sit as to not put unnecessary stress on the joints and base of the Gazebo.
You can set your Gazebo on grass but we recommend that you put pavers under the skids and use shims to level it up
You can put pavers around the complete area where your base will sit.
You can use any crushed gravel to make sure that you have good drainage as we do not want your Gazebo to sit in moisture wet ground.
You can have a concrete slab poured and set your Gazebo on top of the slab or you can order your Gazebo without a floor and bolt you posts to the slab. Please check with us for assistance in determining the required size of the slab and you may want to check with your local building dept. to make sure that they do not have any additional requirements.
Any alterations or changes to your Gazebo should be discussed with an architect.