I use the same ruler as aqua - love it.
If making letters with my cricut I lift my letters directly off the mat with the big paper still there onto drywall tape.
The letters are perfect when they are cut - even and spaced. When I lift them from the same spot with drywall tape they stay that way. If one lifts a little wonky I set it back into the space it came from and lift it again.
THen I glue then or stick to typing paper and take to crop and glue it.
THe drywall tape is loose woven and you can see through it.
I put the glue on the back of each letter and put the drywall tape where I want it. I normally use the clear ruler on the bottom of the letters.
THen I lift the drywall tape up and the glue on the letters keeps them in place.
I can evenly and straightly glue in 5 minutes the type of titles it used to take an hour or more to space and make even.
Wish there were a way to do this with my Slice!