How to define one to many relationship in factory?

Question

• Board has many posts.
• User has many posts.

I want to make dummy posts. I created dummy users and boards. What should I fill in board_id and user_id?

class PostFactory extends Factory
{
    /**
     * Define the model's default state.
     * @return array<string, mixed>
     */
    public function definition()
    {
        return [
            'board_id' => ,
            'user_id' =>, 
            'title' => $this->faker->, 
            'content' => $this->faker->,
        ];
    }
}