Is a foundation necessary for containers? If yes, how?

Ok, so that means you had a distance of approximately 1m between the support points? Then you get to 16 points, I think. That's quite a lot! I can well imagine that you won't have any problems then. That would be roughly 150 kilos per point. Thanks for the tip! How would you support the slabs? With sand? or gravel? crushed stone? and how thick?

Ok, so you had a distance of about 1m between the support points? Then you come to 16 points, I think. That's quite a lot! I can well imagine that you then have no problems. Then it's roughly 150 kilos per point. Thanks for the tip! How would you support the plates from below? With sand? or gravel? crushed stone? and how thick?

Do not support at all. Simply on the natural ground. Surely fewer points would have sufficed. I wanted to be sure it holds because we lived in it. But use something removable, hence no massive foundation.

How would you support the slabs from underneath? With sand? or gravel? crushed stone? and how thick?

If you want it to last permanently and don't have Brandenburg sand, I would make a crushed stone foundation. With our clay soil, it would definitely sink.

I had to set up 3 such containers at my company. I made a "strip foundation" with 30cm deep gravel (compacted) and on top 30x30 paving slabs. It has been standing stable for 5 years. However, it may also be a bit over the top, but the container company demanded it that way.