Final answer:
The best method to create an expansion joint without special materials or tools is to leave a gap, ensuring space for material movement.
Step-by-step explanation:
The best way to make an expansion joint without a plastic strip or tooling is to leave a gap. This allows for the expansion and contraction of construction materials without causing damage. While other methods such as using caulk or applying sealant may provide a temporary solution, these options can fail over time as they may lose adhesion or degrade. Installing a membrane is an alternative method, but it still requires professional installation and isn't simply an expansion joint on its own.