A simple foldable phone stand with print-in-place hinge that can be customized to any length, phone size, or angle of tilt.
I designed the entire model in OpenSCAD, but the original idea isn’t mine. I saw an unbranded, made-in-china phone stand of similar design in the shops here. You can probably buy similar items off ebay for less than a dollar, but this one can be customized to your preference.
The one in the photo was printed in ABS, and others have printed it successfully in PLA (thanks Ben8p!).