what they said, either get someone else to do it, or practice. screw up on enough pieces, buy another sheet of mdf, they're only 20 bucks. i'm only on my 3rd box and it came out ****ed near perfect. however, my first 2 were built around the weird curves and angles of an f-body's rear well area, and the second one was a rather challenging ported build, so when i went to do a square box it was pretty simple by comparison.
what problems were you having, just not able to keep it straight, blade binding up on you?