lay a foundation

verb2

1. •
   To elicit information from a witness to show that the witness has knowledge of a matter before the witness testifies to the matter itself.

   • In order to lay a foundation for the witness to describe the murder, the prosecutor first had to show that the witness was present when the murder occurred.
2. •
   (figurative) To make a start.

   • You should lay a foundation, even if you can't finish the project.