General Idea:
I make prototype tiles like a sandwich made of 4 or 5 pieces of card stock. 4 pieces will come out about 1 mm thick. If the tiles are large (e. g., 2 inches across), you might need 5 or 6 I'd guess, or use paperboard to replace all the center layers.
This method works for a few copies for play testing purposes. I wouldn't want to make a test production run this way.
Materials Needed:
110# Card Stock
1-2mm Paperboard (optional)
Spray Glue (3M Super 77 is recommended) or other Glue
Spray UV Protector Finish (e. g., Krylon) (optional)