Find a location that gets full sun all day. This is important because the sundial uses the shadow cast by an object to indicate the time.
Insert the stick vertically into the ball of clay. At the sunny location, put the stick and clay on the ground or on a table where they won't be disturbed.
On the hour, place a stone at the end of the shadow cast by the stick. Set a timer for 60 minutes. When it rings, go outside, place another stone and immediately reset the timer for another 60 minutes. Continue to do so each hour. The teacher may need to help with the placing of the stones before and after school hours; otherwise, your sundial will be limited to only six or seven hours.
Use your sundial to tell time. You won't make a complete circle of stones because a sundial doesn't work at night. Make sure the students realize this when you give your lesson about the project. If you took time before you began the project to monitor the sun, stick and shadow, you will probably be able to get within about 15 minutes of the correct time.