This project is easy to make. Apart from the fun kids can have, spying on others from around corners etc., it’s also quite educational. For example, the relative angles at which light arrives at and reflects off a surface will likely become clear without the child having to be told. Also, the dimensions of the mirror, if you are cutting it yourself, can be worked out by mathematics. At least it’s one practical use they can see for the formulas they’ll learn in school.
The cutout for it will look something like the following. The dimensions will depend on the mirrors you have available.
You might be able to find some small make-up mirrors of a suitable size. We cut them at 48mm wide, 68mm long, giving us a 50mm square body (allowing some space inside for errors.) The square cutouts are glued over the top and bottom. The body can be glued or sticky-taped together. The mirrors are best glued in. A hot-melt glue gun is a convenient and fast way to assemble it all.
And finally it can be painted however the student feels inspired.