Here is a step by step guide on how to make gum paste/fondant flowers for cake decorating. I learned how to do this a couple of months ago, and I was intimidated before I went, but it is quite simple and so I wanted to share.
First, roll out your fondant mat, grease it with Crisco, and grease your hands as well. Get equal amounts of gum paste and fondant, make them both smooth, by mixing in a little Crisco. Also make sure to remove any hard parts, because they will make lumps when you try to roll it out. Combine the fondant and gum paste until it is one uniform mass.
Remember as you go to reapply Crisco to whatever needs it. This mixture (gumpaste/fondant) is very sticky and delicate, and the Crisco helps it not to stick or tear. Grease your small fondant rolling pin and roll out the gumpaste/fondant as thin as you can, also as evenly as you can. You should be able to see the lines of your mat clearly when it is thin enough.
Using your fondant cutter, cut out as many flowers as you can. Make sure you press down firmly, so that the cutter cuts all the way through.
Carefully transfer your flowers to a space where you can keep them covered as you work, so they don't dry out. (The Wilton practice board is perfect for this job.)
Dust your fondant pad (with your dusting bag-filled with 1 Tbls cornstarch and 1 Tbls powdered sugar). Get out your veining tool and working with one flower at a time,
Gently and slowly pull down the petals to curve them and lengthen them. Be careful, if you do this too fast or hard, you can break the petals.
Ahead of time, make your gum glue. 1/4 tsp gumpaste dissolved in 1 Tbls or so of water. Break the gumpaste into little pieces and let it dissolve.
When you are finished with the petals, and have completed 2 flowers, dab the middle of one flower with gum glue
And press another completed flower on top, alternating the petals, in between one another, so it looks like this.