White paper is not so good, because it contains optical brighteners, which distort the result. Better suited is a natural paper, without brighteners. This looks somewhat grayish. White porcelain is also very suitable. But possibly wise it is too bright.
If you have a gray card or something similar, at hand, you should already do the white balance in the camera.
Surprisingly, the eyedropper also works quite well, even if there are no neutral objects in the image, if you capture the whole image. And if this automatic changes the colors too much or too little, then you can readjust very excellently with the slider: “Color temperature”: Warmer or colder, depending on how you want the image.