A plastic shed will not require as much support as a wooden shed, but it is still important to have a solid foundation to ensure the shed remains level and stable. There are several options for the foundation of a plastic shed, including:

1. Concrete slab: A concrete slab is a strong and durable foundation option for a plastic shed. It requires a bit of work to prepare the site and pour the slab, but it will provide a solid foundation that will last for many years.

2. Gravel base: A gravel base is an affordable and easy-to-install option for a plastic shed foundation. To create a gravel base, you will need to level the ground and then add a layer of gravel. The shed can then be placed directly on top of the gravel.

3. Wood frame: A wood frame foundation is another option for a plastic shed. To create a wood frame foundation, you will need to build a frame out of treated lumber and then place the shed on top of the frame. This option is less durable than a concrete slab or gravel base, but it can be a good choice if you need to move the shed in the future.

It is important to choose a foundation option that is appropriate for the size and weight of your plastic shed, as well as the type of ground on which it will be placed. It may also be a good idea to consult with a professional or refer to the manufacturer's recommendations for the specific shed you are using.