Create a demo that showcases how triangle trade works. Choose one item that needs at least three parties to create and that everyone needs (e.g. a pen). Person X has all of the ink supplies, Person Y has all of the casings for the pens, and Person Z has the lids to finish the pens off. Y buys ink from X, and Z buys the ink with the casings from Y and sells them back to X and Y. Ultimately, X is exploited, Y 's position stays roughly the same, and Z makes a tidy profit. The reason for the profit differential is the education (or steps) required in making the product (e.g. compare the value of iron to a car in the real world). Try the demo with items other than a pen as well.
A poster exploring a historical triangle trade interaction or a theoretical explanation of how it works would also be effective. One example of a historical triangle interaction is the Atlantic slave trade from the 15th to late 19th centuries. The poster could include the main parties of the trade (i.e. America, Europe, and West Africa), and draw arrows between them geographically helping to explain how the trade worked. A theoretical explanation would explain in principle how a triangle trade was possible and on the poster you might include either a list detailing aspects of a triangle trade and/or a full diagram exploring one theoretical example of a triangle trade (e.g. the pen example from Section).
Creating a model of the Atlantic slave trade or another example of a triangle trade would also be effective. For a more simple showcasing of people interacting with one another, consider using kingdoms made of Legos with Lego figurines trading with each other to explore how a triangle trade works. For more advanced models, you will likely need to study model-making concepts such as notions of scale and balance before venturing forth with figurines and model-making equipment (e.g. a hot glue gun, sand paper, and scrap materials).