I wanted a small (2200mm x 2200mm x 80mm) olympic lifting platform, durable enough to cope with weights in exceed of the current master records, which can be deassembled with little effort and does not cost more than 300--400 EUR.
That rules out any platform I could buy, besides a professional lifting platform goes for north of 3000 EUR over here... So it's construction time; first let's see how the base layer of a professional platform looks like and lets estimate what a platform build on this design would cost.
Usually the base layer is build from as many 100mm x 50--60mm x 2200--4000mm wooden beams (connected with iron rods) as needed to cover the area of the platform. For a 2200mm x 2200mm platform that would translate into approximately 100m of 100mm x 50mm beams---which cost around 8 EUR per m, so the ground layer would cost approx. 800 EUR alone... Not an option for me, so out with this design...
Unfortunately I could not use the simple solution: two layers of rubber with a center layer of wood, everything hold together with an outer wooden frame---the ground the platform will stand is not level. Also I may move in a couple of years and indoors a solid fundament will help to dissipate the impact of the dropping weights.
Therefore I opted for a durable fundament made from wood board layers. I did not opt for big wood cheets as I may need to store these and big wood cheets may warp when stored. Using smaller boards has finally the advantage that in the unlikely case one breaks it will be easy and cheap to replace it.