I use Dave's idea for alignment. I usually create a template out of 1/8 MDF or birch. I have even made a template to use with my router (pattern following bit) on my laser. I needed to stack and glue the MDF though, because I needed 3/4 depth. I also used 1/4" acrylic because I ran out of MDF.

MDF is cheap enough, I use it for templates and for practicing (to see if I did alignments right)

Shaddy