My advice would be to leave the home, and take pictures outside. The iPhone 7's camera isn't nearly as good as the 10 and onwards, which argues against taking photos indoors. You can use a sheet of paper to prevent glare—hold it over the watch until the glare doesn't show. Now, also be aware that some crystals are notoriously hard to photograph well, particularly domed ones. Glare is more or less inevitable there. Good luck, hope it works out!