How to do I set the default value for a member of the type BOOLEAN_FIELD in a derived class from foundry.abstract.DocumentData in foundry vvt?

Is there a hook / overwriteable function, when a placeable foundry vvt object was succesfully added to the scene and is ready to be used?

calling

const myown_data = { give_me_icecream: true }
canvas.scene.updateEmbeddedDocuments('ContainerName',[{ _id: this.data._id, ...myown_data }])

in

 _onCreate

complains that the data could not be written / saved when I create the object. But when I reload the scene the data is written to all objects of the type without a problem. I would like to just to set some default values for a BOOLEAN_FIELD or any other DocumentField in a foundry.abstract.DocumentData Class, which should be used only when the object is created for the first time.