How do you build a garden bench?

How do you build a garden bench?
Pour in concrete in 3 boxes ("concrete molds", you can buy these or make them yourself.) Join the parts with some more concrete, finish and install the bench. The total can be less than $20.
If you prefer a wooden bench, the easiest way to do it is with trunks.

If you want more specific answers, you'd better specify what kind of garden bench you want to build.