Start with a small plain box (any colour and shape you like). They can be found in many craft shops.
Either print or draw out a christmassy stencil and then cut it out neatly.
Make sure the stencil is placed in the correct place (middle and straight) before drawing around it.
Use a small paintbrush and paint inside the shape with PVA glue (make sure you don't go outside the lines.
Now get your glitter!! (red, silver, white or gold work great for a Christmas theme).
While the glue is still wet, sprinkle the glitter all over the glue making sure you don't miss anywhere.
Tip off the excess glitter.
Knock the box gently on the table making sure all the excess glitter is removed.
Once the glue is dry (in 1-2 hours) you are ready to use your gift box!