All you need is a medium to large potato.
Cut the end off the potato
and on the cut end draw the outline of a clover leaf.
Using a table knife (for safety)
carefully carve away the excess potato down
about an inch until only the shamrock remains.
Use the potato like a stamp with an ink pad or thinned paint
(either of them will do. But the color should be green)
Now decorate paper or cards with these stamps for St. Patrick's Day.
Try out the other sections