When my boy started to sit unsupportedly, I trained him to use the potty.
So far, he is ok with it.
Since he has some "sign" when he needs to poh, so it is rather easy for us to spot and put him in his potty.
Try la, baby needs to do thing repeatedly. If once doesn't work, do it again, if not succesful yet, try again and again and again. Eventually, baby knows what to do when. Remember, their brain is empty and has a lot of room for training.