But, surely you know about mummies, yes? Mummification has happened accidentally, including Ötzi.
Bodies are found in peat bogs which have been there for 2,000 years, like https://en.wikipedia.org/wiki/Huldremose_Woman . See https://en.wikipedia.org/wiki/List_of_bog_bodies .
And it isn't that the organic material doesn't decay, but that fossilization occurs before substantial decay. The first paragraph in the Lagerstätte page even says:
> These formations may have resulted from carcass burial in an anoxic environment with minimal bacteria, thus delaying the decomposition of both gross and fine biological features until long after a durable impression was created in the surrounding matrix.
so, no, they weren't "preserved on the surface of a rock", but buried, then fossilized.
In the fish image, the upper layer then forms its own layer of stone. In the Green River Formation, the split fish layer can "easily split along the layers to reveal the fossils" - https://en.wikipedia.org/wiki/Green_River_Formation
If you don't understand the topic, that's fine. But to reject a description under the guise of skepticism, without honestly engaging in the material, is not.