I made some paper dahlias last week (click here for the video) so I decided to make one out of gumpaste to go with them.
I started with a 1" styrofoam ball center on a wire, covered it with some gumpaste, then used a sunflower/gerbera cutter to cut out some small petals to put around the ball. Extend them up onto the center, and keep doing rows of those that extend down the side of the ball until you have three or four layers.
Either using a small gerbera cutter, or any small petal that's kind of daisy petal shaped (I used the two smallest ones in a poinsettia set), cut out about twelve each of a small petal and one that's slightly larger.
Curve the petal by using a veining tool and rolling it on the petal. The rolled end is the end that attaches to the base of the flower, so leave the top of the petal a little more open and the base a little more rolled.
Attach the smaller petals around the wired ball, then attach another row of the larger ones. Let that flower dry, it will be the center of the large flower. Or just add another row of larger petals and call it a day.
Now use three larger petal cutters to make rows of overlapping petals. I started with a round disc of gumpaste to attach the petals to, and a daylily petal cutter. Put the disc in a piece of tinfoil and curve the foil up to create a saucer-type shape to dry the flower in.
I gum-glued a circle of the largest petal, then another one, then one row each of two smaller lily cutter petals on top of those. Roll the inside of the petals where they attach a little to give them a curved appearance, and twist the ends of the petals so that they don't lie flat against each other. Put small pieces of tissue or plastic wrap between the ends of the petals to help them dry in the curved shapes.
When the flower is as big as you want it (and you can do more or fewer rows of exterior petals, it's totally up to you), put some gum glue in the center and insert the wire of the center flower through the middle of the larger petals. pull it down firmly and press it to make sure they stick together.
Leave all of the tissue in place while the flower is drying, which is going to take a decent amount of time. This one is so big I'm going to leave it for a few days. You can remove the tissue bit by bit as it sets up so that more air can circulate into the flower to help dry it, but it's better to leave the larger flowers for a long time so that they're definitely dry when you start messing around with them.