Random FYI: Michaels is starting to carry a Q-Snap like frame for fairly OK prices (get the 50% coupon and they are affordable). I think their brand is called "Loops and Threads" or something like that. They appear to be sold in a plastic bag with a blue header that features black text.
I have not yet tried them, nor do I own Q-Snaps, so I don't know how great their brand is.
Are you stitching on Aida or Linen or Evenweave?
In particular I know Linen needs a very high temperature for ironing to work well.
I found getting the creases out works the best if you make sure to iron the fabric on top of a fluffy towel on the ironing board. The iron also has to be on one of the hotter settings, and it works the best after spritzing the fabric with a little water. You might need to make more than one pass, and it does help to flip the fabric over and iron both sides.
Just make sure your fabric is a natural fiber, and nothing that will melt if you are using a higher heat setting.
Otherwise, if it is a small piece, find a really large and heavy book. Phone books are great, since they are free and you can find them everywhere. Insert the fabric flat in the middle of the book- put a piece of clean white paper on either side of it to prevent ink smudges. Then pile one or two other books on top of it and leave them alone for a few days. Wrinkles tend to come out fairly well that way. You can also press flowers in phone books!