Hi Veronica-
I used foam because of the size. The big foam sheets are a better size for a “keeper” placemat. I’m sure you could use construction paper or card stock as well, although they would produce a smaller placemat.
And yes, I used clear contact paper to “laminate” the placemats for use. It worked just fine. I did the laminating at home and returned the placemats to the children the next week.
Best to you,
Nancy