Great advice already.
To reduce unwanted reflection and to get a more even look on reflective parts, like bezel inserts and crystals I will use a black piece of card stock taped to my phone. There's's a cutout in the black card for the camera lens to look through. You can get a nice even lighting look with no reflection of your fingers or your phone visible.
Just took this photo with my phone sitting next to a window.
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This black card was taped to my phone which is one reason you can't see me, or my phone, or the interior of my house reflected in the crystal.
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