Loads of pics here
First we had to set some cavity blocks. There’s quite a slope on TOG’s yard so the left side was about 20mm lower than the right. The left side blocks had to be raised to compensate. After the bottom 4 blocks were set, the others were simply stacked on top. Lengths of timber, painted with bitumen paint for waterproofing, were laid across the top, Now we had a suitable platform to build on.