This is how you make a plant pot out of plaster.

Supplies

To make the mold:

- High impact polystyrene

- Tape

- Pencil

- Ruler

- Cutter

To make the plaster:

- Plaster of Paris

- Water

- Cup around the size of a yogurt container (for measuring)

Step 1: Net

Start by recreating the net shown in the picture on your high impact polystyrene. First using your pencil and ruler, create a 3x3 grid; each grid being 7cmx7cm. Next, draw crosses on each box(except for the center), this creates 4 triangles in each grid. Then, scribble out the areas shown in the picture, the scribbled parts are the parts that are not part of our net.

Step 2: Cut and Score

Cut out the areas that we scribbled since it is not part of our net. Use a ruler and a cutter to accurately cut it out. It should look something like the picture above.

Now that you have cut out your net, use the cutter and ruler to score out the lines that you drew on the net. To score only run the cutter over the line once or twice. This enables the high impact polystyrene to bend into the shape you want.

Step 3: Building

The square in the center of the net is the bottom of our mold. So, fold all four sides of it up and tape it. Now work on each flap one at a time. In the first picture, you can see that the edge is already folded up, next you have to fold the next line that you scored outwards like in the second picture. Thirdly, fold the horizontal line inwards and then fold the last line outwards. As your folding make sure to tape your fold at the same time. If you high impact polystyrene snaps and breaks then it is fine, just tape it back together. Repeat this process three more times.

Step 4: Finishing Mold

After you taped all the flaps(edges), join them all together by taping them. A square should be formed on the opening. Once the shape is created, you should tape all the corners and edges you might have missed. There should be no holes left or else the plaster will leak.

Step 5: Core

To make the core which will be used to create a hole for your plant, you have to create a net. Draw four 10cmx3cm rectangles side by side and a 3cmx3cm square. Cut and score them as you did with the mold.

Step 6: Core

Fold all the lines that you drew/scored and tape the width onto the square piece, this will create a rectangular prism with an opening. To insure plaster will not leak into the core, tape up the sides and corners so that there are no holes left.

Step 7: Pouring

Now that your mold and core are finished you can pour. Using your cup, measure two cups of water and three cups of plaster of paris. Pour in the water first and then mix them together until combined. Once combined, pour the mixture into your mold; leave some space so when you put in your core the plaster mixture does not overflow. Place your core in the center of the mold and use tape to secure it. Make sure you leave some space at the bottom of the mold because you want your pot to have a bottom. After you are done let the plaster dry out for at least 45 minutes.

Step 8: Finishing

Once your plaster has dried, remove the mold with a cutter.

Your plaster will come out a bit rough, so when it is dried you should sand it. Start with the sandpaper that is the most abrasive and slowly change to the finest one. This will leave your plant pot smooth. Once you're done with this step you are finished with your plant pot.