Have a pizza while you read the rest of these instructions.
Step 1: Materials and tools.
The polystyrene disc from under a store-bought pizza.
Sharp knife ("X-acto" or similar. The ones I use come under the heading of "similar" - they cost me Â£1.99 ($3-$4) from my local Morrisons Supermarket).
Sticky tape. You may need to use duct tape: if your pizza base is greasy, normal tape sometimes won't stick.
Optional: paper template. I needed to use the template because my pizza base was black, and so is my pen. Some bases are white, and you can draw your pattern directly onto them.