Cookie stamps are made using 6mm thick acrylic.  You can either use it as is, or give it a touch of colour with the edible food colour of your choice, for a contrasting finish.
 
How to get the best results from your debosser:
Sprinkle a little flour over the embosser to avoid the fondant sticking to it.
Roll out your fondant as per usual. 
Lay the embosser on the bench and lay your fondant over the top of it.
Roll your fondant onto the embosser using a rolling pin. 
 
Standard size is 8cmx8cm square. If you require a different size please let me know.
Hand wash with warm soapy water.