I have attached a image. I am trying to get such effect on flutter. Can anyone tell how such effects are created?

You can either directly create this kind of image using your picture editor (PS, Figma, Paint, anything really). Add manually a margin to your Card and set the Runner for it to be out of the Card. Then simply display the picture file in Flutter using Image.assets(...).

In the case you want to programmatically create a similar image you can use a Stack in Flutter in order to make the runner picture overflow the card positioning manually both pictures.