A very popular lesson with both my students and parents which yield fantastic results for all kids.
I teach this to Grades 4 through 6. We use cereal boxes as a base but any cardstock would work as well.
We also use just regular yarn (any colours, doesn't matter) and white glue.
Cut the yarn and glue down whatever design you like. I just tell kids that the design has to have all enclosed shapes (nothing open). This is a great lesson to teach line and shape. Let dry overnight.
The cardboard will curl a bit but that's ok.
Cover the whole image with a thick layer of glue stick and glue on a piece of tin foil that's about an inch larger on all sides. Rub it carefully, starting from the center and working your way out. We use small pieces of felt to carefully emboss all the edges. Take your time with this step- it is the key to a nice crisp design. Then colour with sharpies, leaving the raised yarn part un-coloured (or silver)
Some finished pieces: