Question

how might an entire insect be preserved?
soft and hard tissues turn the insect into rock.
tree sap flows over the insect and hardens.
sediment accumulates over the insect and hardens.
carbon from the decaying insect leaves a print on a rock.

Explanation:

When tree sap (resin) flows over an insect and hardens (forming amber), it can preserve the entire insect. This is a common way for insects to be fossilized with their soft and hard parts intact. In the case of soft and hard tissues turning into rock (mineral replacement), it usually doesn't preserve the entire insect as a whole entity in the way amber does. Sediment accumulation (like in sedimentary rock formation through compaction and cementation) often doesn't preserve the insect's details as well as amber. Carbon from decaying insect leaving a print (carbonization) mainly leaves a thin carbon - rich film (a print) rather than preserving the entire insect.

Answer:

Tree sap flows over the insect and hardens.