What kind of incubator do you have? I wouldn't put a towel in the bottom its will get all poopy. But that's with my incubator. The eggs should stop turning three days before e. When they go into lock down put the humidity up some.
That's what mine is like. And if you are worried about keeping eggs in the right position which I usually try to do( I'm not sure if its necessary) I put them in egg cartons when going into lock down.
Would a towel interfere with air circulation and heating? Some incubators have the fan or heat source at the bottom so a towel would not be a good idea. If the fan and heat are at the incubator top, a towel can be used. What's important here, is that the material under the eggs provide traction for the hatching chicks so they can keep their legs and feet under them. Paper toweling works and is disposable. I like to use fine meshed plastic screen. What matters is that the chicks not hatch on a slippery surface, because when they do, spraddle leg develops; where the legs and feet deform out to the sides. When this happens the chicks can't walk and it's not always easy to correct; if at all.
Then you do not have to put anything under the eggs.
You're welcome and good luck!
