Examine a russet potato and look for a section of the potato that has the most eyes, or buds. These look like dimples in the potatoes. When you find a suitable section with the most buds, cut that section of the potato off with a sharp knife, separating it from the rest of the potato.
Stick toothpicks all over the top of the sliced potato piece, piercing the buds. Space the toothpicks evenly around the potato.
Fill a plastic bowl with room temperature water. Stick the potato into the water with the toothpicks facing down. The toothpicks should touch the bottom of the bowl, and the water should come up high enough to just touch the skin of the potato. Do not completely drown the potato. According to the University of Florida, potatoes do not grow in flooded conditions.
Set the bowl beneath a window so that the potato can get sun but do not cover the potato or the bowl.
Monitor the changes of the potato over the course of a few weeks. You will start to notice that the buds begin to sprout new potato plants that come up from the toothpicks. Roots will also begin to grow below.
Remove the toothpicks once the new sprouts are visible. If you leave the potato in the plastic bowl, it will continue to grow. Or, you can keep the roots intact and transport it into a pot with soil to move it.