Ok all you professional cake people out there...
I've been working with fondant for the past 2 years and I STILL can't figure out how to avoid these wrinkles (shown below) at the bottom of my cakes.

HOW do I avoid these??? I've tried changing fondant brands, kneading out my fondant enough to reach that nice piable stage but not TOO much, etc etc. It's really frustrating me, and all my reading on it isn't helping.
Thanks!

Is this occuring immediately or later on after the cake has sat covered for a while?

Hmmm, it looks like elephant skin to me. I find that elevating the cake on top of something small helps. Also, this happens when I work(roll) too long and my fondant tends to dry a bit.

it's definitely happening immediately. it's almost like the fondant just has nowhere to go, so i have to let it bunch up at the bottom. I do have a REALLY bad rolling pin, so rolling it out too long could be the problem. If you have any other suggestions, let me know!

What do you sit your cake on when you put the fondant on? Is it sitting flat on the table or counter? I elevate mine like Rylan said so that the fondant falls away from the cake at the bottom. For instance, if I'm covering an 8 inch cake I will set it on a 6 inch baking pan so that it's not flush with the counter. Hope this makes sense. I'm not very good at explaing things

I agree - pop your cake tier on a smaller support round (or square) like an upturned baking tin. You can still place that on top of your turntable. I only get the dreaded elephant skin when I have too much fondant folding out at the bottom.

On my first cake, I got creases because my fondant piece wasn't large enough.
Even though technically it fit and covered the entire cake, there wasn't enough excess at the bottom, which would've allowed for the lifting and smoothing that was necessary.

This also tends to happen to me when my fondant is too dry. By the time I get to the edges the fondant has already dried and doesn't go on smoothly. You could try softening the fondant (by adding shortening, glycerin, or glucose). Or if the fondant is already on the cake, try rubbing in a little shortening or water on the lines and smooth it out.

Are you cutting it from both directions? It almost looks like it is getting pinched from both sides. I'm new to cake decorating, but have you tried cutting with a pizza cutter at a 45 degree angle in one direction all the way around? Anyway, just a thought.

When you raise the cake on a platform how do you trim off the bottom edge?

I find it was much easier to watch youtube tutorials on how to cover a cake in fondant. I think the first instinct is to smooth one section at a time (that's how I got wrinkling on the bottom on my first cakes) but they show you that it's best to smooth from the top then work your way down gradually and very lightly stretching out the fondant on the bottom when when you see creases before you actually use your smoother to smooth the bottom sides.

Forgot to mention too, when you are elevating the cake on a platform, be careful of the weight of the fondant wanting to tear around the top edge. You do need to support it carefully and work swiftly frm top to bottom.

Pink Lisa - once I have the cake essentially covered I quickly and not neatly cut (knife) just below the bottom edge, then smooth the sides carefully, and finally trim with a sharp knife right on the bottom edge of the cardboard. HTH.