Potato stamping is a great activity that most of us have done in our childhood, why don't you have a go at this with your children this halloween?
I took the smallest potato in the bag and cut it diagonally to give me a wide surface area. Then using a knife I carefully carved out my skull and a bone. The skull is fairly easy to make. The shape is made by cutting an inverted curve out of the potato to create that gaunt look. Then either with a knife or the top of a potato peeler you can create the eyes.
The bone is a little trickier and it needs to be raised up. It sliced my main bone lines and carefully slid my knife horizontally through that part of the potato, removing the excess piece.
Make sure your potato is dry - pat it with a tea towel.
Use either a printing paint or something like acrylic. Acrylics will give a more uniform effect to the print. I used block printing water colour hence the unevenness in print. You can use a brayer or just spread the paint thinly on something flat (I used a coaster). Dip the potato in paint (or use the brayer to apply it) and stamp carefully onto your paper. I advise testing it out on some scrap paper first.
I used my print to make a card for a boy.