When both parts are printed use a hairdryer, heat gun or another heat source to make the base flexible and put the pot into it and move it around, this will mean that there would be a good fit between pot and base. A good plant is one that is not to big, so that the pot doesn't fall over. The models can be scaled up/down for different plants and plant size.
After printed fill the base 1/3 with water and place the plant pot into it.

sorry about typo with Base file