Automatic effects Confirmation needed (Flesh of Marble)

Rémi wrote:

Dear all,

If there is an automatic effect that should trigger, can you please confirm that there is a window to use non automatic effect first?

*nitpicking on*
"Confirm" implies that the assertion is right. I don't think it's the right term to use when asking a question.
As it is, I cannot confirm something that is wrong.

Rémi wrote:

My plays Flesh of Marble, then recieve 1 damage during the current round of combat.
When they recieve more damage, is there a window to activate prevent effects before Flesh of Marble automaticly prevent all that damage.

I assume you mean you take a total of X damage at the same time (rather than 1, then later on, a new batch of damage).
When receiving damage, you can choose to prevent it or not. If you don't, the first damage is applied as usual, then the rest is automatically prevented by FoM.
Once FoM has kicked in, it's too late to play other means of prevention, since you cannot prevent damage that is already prevented.