Eating mini pies as a math teacher is a challenge because they are made for one. Students stop working and watch with envy as you enjoy the small layered crust and still warm fruit filling.
Wouldn't it be better if you created a small circular cardboard cave to recede into and enjoy your pie in peace and quiet? This Pi/pie cave is the perfect solution. Make one yourself and be a classroom (or office) "Pi"oneer!

Step 1: Supplies.

1) You will need lots of cardboard. The circle supports should be made of a single piece of heavy cardboard.
2) Duct tape is used to seam pieces together.
3) A box knife separates and shapes segments.
4) String and a marker can be used as a makeshift compass for making perfect circles.

During this step, find someone to bake you a mini pie. Direct them to one of the great instructables on making pie.

Step 2: Support Semi-circles

Take 2 large sturdy cardboard pieces. Use a string at the centre point of the base and hold a marker to the string at the edge of the base. Move the marker across the cardboard keeping tension.
The string acts as a radius and creates a half circle on the cardboard approximately 3.1415926 times its length.
Math is fun.
If possible, leave a flap of cardboard below. Attach a support brace to the cardboard semi-circle with lots of duct tape.

Step 3: Cave Walls

Use a large box and cut one edge so it becomes a flat rectangle. Duct tape the box tops and bottoms so it holds the rectangle shape.
Put the cardboard on a soft surface and walk on it to break down the rigidity of the cardboard. This will help it to bend to the shape of the semi-circle supports.

More math: The half cylinder walls should be the same height as the half circumference of the supports (if you want the cave to be whole.) Ours is open at the bottom. The net of a cylinder is a circle attached to a same height rectangle. Lots of potential learning in these proportions. Have someone calculate all the sizes and proportions while you eat pie in your cave.

Step 4: Assembly

Attach the cave walls to the semi-circle supports with duct tape.
You will need lots of tape and lots of hands and some patience.

We found that the cave needed a centre support so we used the same sharpie and string to make an identical centre support.

At this point, someone should have baked you a pie to reward your efforts. Stealthily take the pie and hide in your cave to enjoy it away from prying eyes.