Get an acrylic block that the stamp will completely fit on but isn't sooo big that the block wobbles when you put it down. Make sense? For alphabet letters a 1x1 is good. For stamps the size of say, In Full Bloom, a 2x2 works. When you mount to the static cling material, do take off the foam already on the rubber. You can often just peel this off. If needed you can microwave it for 10 sec or so to loosen the adhesive.
For blocks and mounting foam TAC has a block starter kit for $14. This has one each of 1x1, 4 3/4x7, 2x2, 4 3/4x4 3/4, 1 1/2x4 3/4
Or a mini starter for $5.95 that has one each of 1x1, 2x2, 3x3, 1 1/2x1 1/2
Creative Cling (8x10) is $5 and you can get 20 to 40 stamps on one sheet depending on size.
Another company is
www.sundayinternational.net They have blocks and cling as well but I'm not sure about prices.
Hope that helps!
Fritz
TAC angel #2542