Actually, the hollow-core door and ceiling tile are often used together.

You need to start with a hard, FLAT surface. Most people suggest a hollow-core door because they are easy to find and relatively inexpensive, but a piece of counter top, or ANY good, flat surface will work fine.

Some people like to pin parts to the plans (I prefer to use weights and some use magnets) so laying a ceiling tile on top of your table will allow you to push pins into it.