This project is a perfect example of why we never throw away a shoe box. They are just so great for so many different things!
To make your DIY smartphone projector grab a shoe box. Shoe boxes with dark insides work best, however you could always add some black paper or paint to adapt a lighter coloured box.
Working with the short side of the shoe box, trace around the outer edge of the magnifying lens. You might want to detach the handle from the lens of the magnifying glass first.