I am trying to make a plaque type decoration to stand at the top of a cake and am new to fondant. I have used Wilton fondant with gum tex added which I have done when making a bow. The plaque is still soft enough that it slowly folds over. Any suggestions?

how long did you leave it to dry?

You could start over with fondant that you've added more gum tex to, it doesn't sound like you added enough, or wait a day or two and it will dry. You might need to turn it over so the back can dry once the front has dried, if that will work with your design.

Thanks for the tips. It has been drying all day today and doesn't seem to be stiffening at all. I will let it sit for a couple more days and see what happens. What about color flow?

Let it sit overnight at least. If it's thin then that will probably be long enough, if it's really thick it could take up to a week. If you're in a big hurry for it, you could cut a piece of foam board and then cover that with the fondant. That would dry faster.