3.  Acrylic blocks and stamp positioners:
     a.  Acrylic blocks hold your clear and cling stamps so you can make a crisp and clear image.  There are lots of brands on the market.  What to look for is a set with a variety of sizes and lines on the blocks to help position your stamped image on your paper.  Fiskars Block Set

     b.  Stamp Positioners:  They help to align your stamped images when you want to stamp more then once or if you have a layered stamp set to align.
          1.  Stamp a Ma Jig:  an oldie but a goodie: Stamp-a-ma-jig Amazon
         
          2.  There are a few postioners that are an acrylic block with foam legs that raise the stamp above the paper for easier positioning.  Fiskars has the most popular model:  Fiskars Easy Stamp Press on Amazon

         3.  The most expensive and most adored stamp positioner is the Misti:  Misti Stamping Press-I have it and I love it but I would say you should know you love stamping as a hobby and will be a long time stamping enthusiast before you invest in this tool.  I will add that many people have come up with various Misti copies and are happy with them at a more affordable price tag.