I am part of a non-profit organization that runs a disc golf course (frisbee golf) in southern Sweden. We are currently upgrading our tee pads.
Our basic construction looks like this and is built like a small deck with 45x145 joists in the frame:
The platforms can vary between 3x2m to 5x2m in size.
Most are on fairly level ground, and we have built them loosely laid on concrete slabs. Due to the use of the area, exact leveling isn't crucial. Additionally, the entire structure is pretty much covered with artificial grass, so we're not too concerned if something starts to grow underneath.
Now to the question!
In some places, however, we need to raise the platforms as they sometimes are on hills and sometimes on slopes. Since our courses are out in the woods and we are a small group building them, I am looking for the most efficient way to anchor posts (instead of stone slabs) on slopes like in the image below. We essentially need to carry all the materials to the site and have limited access to tools and other resources. Stability is more important than having everything perfectly straight if compromises are necessary. If it shifts slightly with the seasons, it's acceptable, within certain margins.
All tips and ideas are welcome, both conventional and unconventional methods. As mentioned, simple execution is a priority.