How to build a shed on my existing concrete patio so water does not go under floor base?

My house has a big concrete area that previous owners used for playing basketball. I want to built a basic shed but can't find youtube videos on how to keep water from going under floor base. All the videos are for slabs but I want to know how to build it on concrete floor. hopefully this makes sense. thanks... show more My house has a big concrete area that previous owners used for playing basketball. I want to built a basic shed but can't find youtube videos on how to keep water from going under floor base. All the videos are for slabs but I want to know how to build it on concrete floor. hopefully this makes sense. thanks for reading.
Update: how do i add picture?
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