For the easiest smartphone workflow, try Google PhotoScan (on Android), which is designed for copying printed photos. It can help reduce glare and perspective issues, though quality is still usually below a true flatbed scanner.

For the best results with a phone:

• Don’t use flash.
• Use soft ambient light, such as near a window, but avoid direct sunlight.
• Keep the phone parallel to the print to avoid distortion.
• Don’t shoot extremely close; leave some space and crop afterward.
• Hold the print flat. A clean sheet of glass can help, but watch for reflections.
• If possible, make a simple copy stand or support so the camera points straight down at the photo.

A more traditional setup is to photograph the print on a copy stand with lights placed at roughly 45° angles to reduce reflections. Polarizing filters can also help cut glare.

If the goal is the highest quality, a scanner is still better than photographing the print, but for Facebook and casual sharing, a careful smartphone setup can work well.