Tip 1: Start with the right fondant
Tip 2: Get your icing as smooth as possible The icing on your cake (under the fondant) should be as smooth and hard as possible. For this reason, many people really like working with ganache under fondant. You can get it as smooth as glass and it sets up as hard as a rock. I like ganache, but it's really rich and expensive so I mostly work with meringue buttercreams under my fondant which also provide a nice smooth surface. I use metal bench scraper and an icing spatula to get my buttercream smooth before I apply my fondant.
Tip 3: Knead your fondant in pieces I divide my fondant into several pieces to knead it. Then I zap each piece in the microwave for two 5-second increments to soften it slighty (no more than 5 seconds per zap or you'll melt it!) and then I work it on the counter. I keep the other chunks wrapped in plastic wrap so that they don't get dry and crusty while I work.
While I'm kneading each section, I add a dollop of shortening and a dollop of glycerine to soften the fondant and make it smoother and more pliable. The shortening also helps the fondant to be less sticky. That way, you can use less corn starch (or powdered sugar) when you're rolling. Corn starch and powdered sugar leave white stuff everywhere and can dry out your fondant.
Tip 4: Put away the spray bottle I had always read that you should spray the cake with water (after frosting) before putting the fondant on. This never worked properly for me. The coverage was always uneven, with some spots too wet and some too dry, and the fondant was always slipping around and gooey. What a mess! Then I watched someone apply piping gel with a pastry brush on youtube. Ding! I don't generally have piping gel on hand, but the pastry brush works perfectly. I generally use water with a small amount of tylose powder dissolved in it (which is what I use to adhere pieces of fondant or gumpaste together when making my figures or applying them to the cake). But water works, too. The coverage is nice and even and you can apply it pretty thinly. It also helps do some final smoothing on your cake. Win!
Tip 5: Use your corn starch or powered sugar sparingly Less is more. My preferred anti-stick is corn starch. Really, you don't need much corn starch to keep the fondant from sticking to your counter and rolling pin. I dust just a slight amount on my slightly flattened disc of fondant, rub it around, flip and do the same on the other side. Then I sprinkle a small amount around the countertop where I'll be rolling.
As I roll, I put my hands under and all around the edges to make sure it isn't sticking to the counter. If need be, I sprinkle just a bit underneath and rotate the fondant slightly to distribute.
Tip 6: Roll it out bigger than you think it needs to be Measure your cake across the top and sides. Got that added up? Great, add another 2 inches to the dimension. So if you measured 10 inches across the top and your cake is 3 inches tall, that's 16 inches of cake total. Roll out the fondant to at least 18 inches. I actually like a little more. More fondant along the bottom means you have more to work with when it comes to lifting and smoothing around the bottom and less opportunity for pleating and folding along the bottom.
Tip 7: Roll it up When you're ready to put it onto the cake, roll the whole thing back onto your rolling pin. Don't try to lift it with your arms or your hands and put it onto the cake. You'll get more air bubbles if you try to do it like that. The rolling pin method allows you to roll it slowly over the top of the cake.
Tip 8: Secure the top edges first Once you've rolled it onto the cake, secure all around the very top first. This will prevent the weight of the fondant from pulling away from the edge and tearing your fondant. The other thing that helps prevent fondant from tearing and breaking is the glycerine and shortening you added when you kneaded the fondant earlier as well as using a scant amount of corn starch (or powdered sugar).
Tip 9: Lift up and in Now you're going to work your way down from the top, smoothing out the fondant. Work your way around the cake, smoothing a half inch to an inch at a time all the way around, then keep going around until you get to the bottom. Sounds easy, no? This is the moment of truth. The trick? As you smooth with one hand, use your other hand to lift up the excess fondant on the bottom and push in towards the cake just slightly. It sounds completely counterintuitive, but just try it. Up and in. All that excess will help you with this. Keep lifting as you smooth down.
Tip 10: Cut, smooth, cut Once you've smoothed it all out with your hands all the way around, cut off all the excess with a pizza or pastry cutter.
Then use a fondant smoother to smooth it all down. Push in and move it up and down all around the cake. You'll end up with a little bit more along the bottom edge. Use your cutting wheel to cut it again as close as you can to the bottom edge.
Tip 11: Use a butter knife to get a clean edge Are you always putting something around the bottom of your cake to hide that ragged edge? I take a butter knife and work my way around, using it to gently remove and/or tuck in any excess underneath and create a nice smooth edge.
If there's still a lot you didn't get, use the pizza cutter again. If it's just a tiny bit stuck to the cake board, you can scrape it off the cake board with the butter knife. If there's some that is uneven, use the butter knife to press it gently up into the cake.