Yet another question about concrete bases

[Jon W]

Hi everyone

Sorry to keep asking questions about concrete bases but I keep discovering I don't know quite as much as I thought.

The substrate is red shale. For the most part it is solid or has gouges full of red shale rubble. In order of preference do you think I should;

1. Lay the pad directly over the shale
2. Empty the pits and fill/compact MOT type 1
3. Cover the whole area with compacted MOT type 1.

Cheers

Jon