The premise of this object lesson is that faith is based on our knowledge and experience. That in order to have faith in something, we need to have some knowledge and some experience in that area.
Your objects: 3 small clean pots. 3 items to plant. One of these items needs to be dirt and seeds. The other items need to be like a cookie to be planted in flour, or money to be planted in something, a piece of jewelry to be planted in something. You'll have to give these other items some thought.
The narration could be something like this: I wanted some more cookies just like this one, so I am going to put some flour in this pot, and sugar and plant the cookie. I am going to put some milk and some oil in it everyday and hope that eventually some more cookies will start growing.
I also need some more money, so I have some green paper and some thread and I am going to plant this extra money in the pot and I think I will put some glue and ink in here everyday and I hope that soon a money tree will start to grow.
In this pot, I would enjoy some flowers, so I have some dirt and I am going to put in these seeds. I will put it in the sunshine and water it when it is dry and I have faith that soon, I will have a plant and some flowers.
Do any of you have faith and believe that these two pots will eventually produce cookies or a money tree? And why not? Its because we have knowledge and experience in how cookies are made. We know they don't come from a pot, we have experience that tell us cookies come from our mixing and baking.
For us, money is obtained by working for it, and it comes from the government presses or mints (the place where coins are made). Our knowledge tells us that no matter how much faith we exhibit, it would be a waste of time because money doesn't grow on trees from a pot.
We can and do have faith that a flower will grow from this seed, if given enough water, sunshine and nutrients. That faith is based on our knowledge of how plants work and our experience in planting things. The only reason we would spend any time with the dirt and the pot and the seeds is that we have faith we will get a result from our work.
This is what faith is. A belief in something that is true, that we can't see yet, based on our previous knowledge and experience.

Finish out this discussion with any pertinent scriptures.