We are about one month in to potty training my 21 m old daughter. I was a bit nervous about the pooping b/c she tends to poop while sleeping and I wasn't sure she'd have many chances to poop in the potty. However, my fears were fortunately unfounded.
I agree that she might need to brace her feet on something. Either get a tall stool or get a small potty for her to sit on with her feet on the ground. We have both the family toilet seats and a couple of little potties and sometimes she prefers one over the other.
I tend to be a little more enthusiastic about my celebrations when she poops in the potty vs. peeing. She likes to look at what she's done so I make a big deal about looking at it and seeing it (she'll say "see it" and lean over and get way closer to her poop than I ever want to be, but heck if it keeps her excited about having done it then more power to her! :) )
And then we go together to dump it in the toilet, and she gets to flush and we say "bye bye poop!" and she closes the toilet lid and then opens it again and says "all gone!" So it's a big whoop de do ritual. Maybe once your LO is successful being super celebratory about it will help.
The potty training method we used recommends your LO be naked from the waist down for the first three months after you potty train them whenever you are at home, and when you go out you should only have them in loose fitting pants. Her theory is that undies feel too much like diapers for most LOs. It makes me a little nervous b/c there's nothing to catch the poop if there is an accident, but then again it makes it super easy for my daughter to run to her little red potty and pull up her dress and use it. It saves me full time monitoring, thank goodness!
Good luck!