Garden room base help

[JB808]

I’m building a garden room at the end of my garden, the finishEd size will be 6 m x 4 m. The problem I have is that the area is a mixture of raised stone built beds, patio and soil. In an ideal world I would be able to just build over this as my garden is on a hill and it will be a nightmare trying to get all the spoil to a skip. I’m considering levelling it with a mini digger then smashing up the stone to use as hard-core, thus using up the stone. However this means I will need to get the concrete the full length of the garden for the base. Or would it be easier to put all the stone to one side dig holes for threaded bar foundations then distributing all the stone underneath as a weed barrier. Any thoughts and opinions will be greatly appreciate.
Jim

 

[motorbiking]

Is this an insulated garden room? ie you want to use it all year round? If so, I'd lay an insulated slab. Also make sure its not within 1 meters from the boundary otherwise it needs to be constructed from substantially non-combustable material as you are over 15m2