As the term “flat lay photography” suggests, it’s important to lay your objects out on a surface that is, well, flat. A table or counter will usually do the trick, but your bed or the floor can also work in a pinch! Once you’ve found a relatively flat surface, the only limit to your background is your imagination.
Having said this, it’s generally a good idea to choose a plain, nondescript background that will let your items really “pop”. You might want to tape down some poster paper, lay out a sheet or table cloth, or even roll out some fabric for a textured or themed background.