These are super easy for kids to make and they are so colourful and pretty too.
The backing for them is a square plywood coaster.Children first glue a row of 1cm colourful square tiles along the border of the coaster. They then make another row along the inside. That leaves enough room for four 2cm mirror tiles.
Once the glue is dried, they then apply the grout (I think I used the premade tiler's grout bought at the hardware store), wipe off the excess and leave to dry. Then wipe clean with a damp cloth.
For more details on how to make a mosaic, go here.